2022 | |
Cáceres-Aravena, G; Real, B; D. Guzmán-Silva, ; Amo, A; Foa Torres, L E F; Vicencio, R A Experimental observation of edge states in SSH-Stub photonic lattices Journal Article Open Access Physical Review Research, 4 (013185), 2022. @article{caceres-aravena2022, title = {Experimental observation of edge states in SSH-Stub photonic lattices}, author = {G. C\'{a}ceres-Aravena and B. Real and D. Guzm\'{a}n-Silva, and A. Amo and L. E. F. {Foa Torres} and R. A. Vicencio}, url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.013185}, doi = {10.1103/PhysRevResearch.4.013185}, year = {2022}, date = {2022-03-07}, journal = {Physical Review Research}, volume = {4}, number = {013185}, abstract = {We reveal unconventional edge states in a one-dimensional Stub lattice of coupled waveguides with staggered hoppings. The edge states appear for the same values of hoppings as topological edge states in the Su-Schrieffer-Heeger model. They have different energies depending on the lattice termination and present a remarkable robustness against certain types of disorder. We evidence experimentally the phase transition at which these edge states appear, opening the door to the engineering of one-dimensional lattices with localized edge modes whose energy and location can be controlled at will.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We reveal unconventional edge states in a one-dimensional Stub lattice of coupled waveguides with staggered hoppings. The edge states appear for the same values of hoppings as topological edge states in the Su-Schrieffer-Heeger model. They have different energies depending on the lattice termination and present a remarkable robustness against certain types of disorder. We evidence experimentally the phase transition at which these edge states appear, opening the door to the engineering of one-dimensional lattices with localized edge modes whose energy and location can be controlled at will. | |
Medina Dueñas, J; Calvo, H L; Foa Torres, L E F Copropagating edge states produced by the interaction between electrons and chiral phonons in two-dimensional materials Journal Article Physical Review Letters, 128 , pp. 066801, 2022. @article{medina-duenas2022, title = {Copropagating edge states produced by the interaction between electrons and chiral phonons in two-dimensional materials}, author = {J. {Medina Due\~{n}as} and H. L. Calvo and L. E. F. {Foa Torres}}, url = {https://arxiv.org/abs/2109.03815}, doi = {https://doi.org/10.1103/PhysRevLett.128.066801}, year = {2022}, date = {2022-02-07}, journal = {Physical Review Letters}, volume = {128}, pages = {066801}, abstract = {Unlike the chirality of electrons, the intrinsic chirality of phonons has only surfaced in recent years. Here, we report on the effects of the interaction between electrons and chiral phonons in two-dimensional materials by using a nonperturbative solution. We show that chiral phonons introduce inelastic Umklapp processes resulting in copropagating edge states that coexist with a continuum. Transport simulations further reveal the robustness of the edge states. Our results hint on the possibility of having a metal embedded with hybrid electron-phonon states of matter.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Unlike the chirality of electrons, the intrinsic chirality of phonons has only surfaced in recent years. Here, we report on the effects of the interaction between electrons and chiral phonons in two-dimensional materials by using a nonperturbative solution. We show that chiral phonons introduce inelastic Umklapp processes resulting in copropagating edge states that coexist with a continuum. Transport simulations further reveal the robustness of the edge states. Our results hint on the possibility of having a metal embedded with hybrid electron-phonon states of matter. | |
Mella, J; Foa Torres, L E F Robustness of spin-polarized edge states in a two-dimensional topological semimetal without inversion symmetry Journal Article Physical Review B, 105 , pp. 075403, 2022. @article{mella2021, title = {Robustness of spin-polarized edge states in a two-dimensional topological semimetal without inversion symmetry}, author = {J. Mella and L. E. F. {Foa Torres}}, url = {https://arxiv.org/abs/2107.12956}, doi = {https://doi.org/10.1103/PhysRevB.105.075403}, year = {2022}, date = {2022-01-27}, journal = {Physical Review B}, volume = {105}, pages = {075403}, abstract = {Three-dimensional topological gapless phases have attracted significant attention due to their unique electronic properties. One of the flagships is the Weyl semimetals, which requires breaking time-reversal or inversion symmetry in three dimensions. In two dimensions, the dimensionality reduction requires imposing an additional symmetry, thereby weakening the phase. Like its three-dimensional counterpart, these two-dimensional Weyl semimetals present edge states directly related to Weyl nodes. The direct comparison with the edge states in zigzag-like terminated graphene ribbons is unavoidable, offering the question of how robust these states are and their differences. Here we benchmark the robustness of the edge states in two-dimensional Weyl semimetals with those present in zigzag graphene ribbons. To such end, we use a Dirac Hamiltonian model proposed by Young and Kane, adding new terms for inducing a two-dimensional Weyl semimetal phase and use a scattering picture for the transport calculation. Our results show that despite having a similar electronic band structure, the edge states of two-dimensional Weyl semimetal are more robust against vacancies than graphene ribbons. We attribute this enhanced robustness to a crucial role of the spin degree of freedom in the former case.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Three-dimensional topological gapless phases have attracted significant attention due to their unique electronic properties. One of the flagships is the Weyl semimetals, which requires breaking time-reversal or inversion symmetry in three dimensions. In two dimensions, the dimensionality reduction requires imposing an additional symmetry, thereby weakening the phase. Like its three-dimensional counterpart, these two-dimensional Weyl semimetals present edge states directly related to Weyl nodes. The direct comparison with the edge states in zigzag-like terminated graphene ribbons is unavoidable, offering the question of how robust these states are and their differences. Here we benchmark the robustness of the edge states in two-dimensional Weyl semimetals with those present in zigzag graphene ribbons. To such end, we use a Dirac Hamiltonian model proposed by Young and Kane, adding new terms for inducing a two-dimensional Weyl semimetal phase and use a scattering picture for the transport calculation. Our results show that despite having a similar electronic band structure, the edge states of two-dimensional Weyl semimetal are more robust against vacancies than graphene ribbons. We attribute this enhanced robustness to a crucial role of the spin degree of freedom in the former case. | |
2021 | |
Foa Torres, L E F; Valenzuela, S O A valley of opportunities Journal Article Physics World, 11 , pp. 43, 2021, ISSN: 2058-7058. BibTeX | Links: @article{foatorres_2021_valley, title = {A valley of opportunities}, author = {L. E. F. {Foa Torres} and S. O. Valenzuela}, url = {https://t.co/ybNNHDPFUF}, doi = {https://doi.org/10.1088/2058-7058/34/11/40}, issn = {2058-7058}, year = {2021}, date = {2021-11-01}, journal = {Physics World}, volume = {11}, pages = {43}, keywords = {}, pubstate = {published}, tppubtype = {article} } | |
Medina Duenas, J; Ryan Pérez, G O'; Hermann-Avigliano, Carla; Foa Torres, L E F Quadrature protection of squeezed states in a one-dimensional topological insulator Journal Article Open Access Quantum, 5 , pp. 526, 2021. @article{medina-duenas2021, title = {Quadrature protection of squeezed states in a one-dimensional topological insulator}, author = {J. {Medina Duenas} and G. O'{Ryan P\'{e}rez} and Carla Hermann-Avigliano and L. E. F. {Foa Torres}}, url = {https://arxiv.org/abs/2106.00869}, doi = {10.22331/q-2021-08-17-526}, year = {2021}, date = {2021-08-17}, journal = {Quantum}, volume = {5}, pages = {526}, abstract = {What is the role of topology in the propagation of quantum light in photonic lattices? We address this question by studying the propagation of squeezed states in a topological one-dimensional waveguide array, benchmarking our results with those for a topologically trivial localized state, and studying their robustness against disorder. Specifically, we study photon statistics, one-mode and two-mode squeezing, and entanglement generation when the localized state is excited with squeezed light. These quantum properties inherit the shape of the localized state but, more interestingly, and unlike in the topologically trivial case, we find that propagation of squeezed light in a topologically protected state robustly preserves the phase of the squeezed quadrature as the system evolves. We show how this latter topological advantage can be harnessed for quantum information protocols.}, keywords = {}, pubstate = {published}, tppubtype = {article} } What is the role of topology in the propagation of quantum light in photonic lattices? We address this question by studying the propagation of squeezed states in a topological one-dimensional waveguide array, benchmarking our results with those for a topologically trivial localized state, and studying their robustness against disorder. Specifically, we study photon statistics, one-mode and two-mode squeezing, and entanglement generation when the localized state is excited with squeezed light. These quantum properties inherit the shape of the localized state but, more interestingly, and unlike in the topologically trivial case, we find that propagation of squeezed light in a topologically protected state robustly preserves the phase of the squeezed quadrature as the system evolves. We show how this latter topological advantage can be harnessed for quantum information protocols. | |
Berdakin, M; Rodriguez-Mena, Esteban A; Foa Torres, L E F Spin-polarized tunable photocurrents Journal Article Nano Letters, 21 , pp. 3177, 2021. @article{berdakin2020, title = {Spin-polarized tunable photocurrents}, author = {M Berdakin and Esteban A Rodriguez-Mena and L. E. F. {Foa Torres}}, url = {https://arxiv.org/abs/2010.11883}, doi = {https://doi.org/10.1021/acs.nanolett.1c00420}, year = {2021}, date = {2021-04-05}, journal = {Nano Letters}, volume = {21}, pages = {3177}, abstract = {Harnessing the unique features of topological materials for the development of a new generation of topological based devices is a challenge of paramount importance. Using Floquet scattering theory combined with atomistic models we study the interplay between laser illumination, spin and topology in a two-dimensional material with spin-orbit coupling. Starting from a topological phase, we show how laser illumination can selectively disrupt the topological edge states depending on their spin. This is manifested by the generation of pure spin currents and spin-polarized charge photocurrents under linearly and circularly polarized laser-illumination, respectively. Our results open a path for the generation and control of spin-polarized photocurrents.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Harnessing the unique features of topological materials for the development of a new generation of topological based devices is a challenge of paramount importance. Using Floquet scattering theory combined with atomistic models we study the interplay between laser illumination, spin and topology in a two-dimensional material with spin-orbit coupling. Starting from a topological phase, we show how laser illumination can selectively disrupt the topological edge states depending on their spin. This is manifested by the generation of pure spin currents and spin-polarized charge photocurrents under linearly and circularly polarized laser-illumination, respectively. Our results open a path for the generation and control of spin-polarized photocurrents. | |
Huamán, A; Foa Torres, L E F; Balseiro, C A; Usaj, Gonzalo Quantum Hall edge states under periodic driving: A Floquet induced chirality switch Journal Article Open Access Physical Review Research, 3 , pp. 013201, 2021. @article{huaman2021, title = {Quantum Hall edge states under periodic driving: A Floquet induced chirality switch}, author = {A. Huam\'{a}n and L. E. F. {Foa Torres} and C. A. Balseiro and Gonzalo Usaj}, url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.3.013201}, doi = {10.1103/PhysRevResearch.3.013201}, year = {2021}, date = {2021-03-04}, journal = {Physical Review Research}, volume = {3}, pages = {013201}, abstract = {We report on the fate of the quantum Hall effect in graphene under intense laser illumination. By using Floquet theory combined with both a low energy description and full tight-binding models, we clarify the selection rules, the quasienergy band structure, as well as their connection with the two-terminal and multiterminal conductance in a device setup as relevant for experiments. We show that the well-known dynamical gaps that appear in the Floquet spectrum at ±ℏΩ/2 lead to a switch-off of the quantum Hall edge transport for different edge terminations except for the armchair one, where two terms cancel out exactly. More interestingly, we show that near the Dirac point changing the laser polarization (circular right or circular left) controls the Hall conductance, by allowing to switch it on or off, or even by flipping its sign, thereby reversing the chirality of the edge states. This might lead to new avenues to fully control topologically protected transport.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on the fate of the quantum Hall effect in graphene under intense laser illumination. By using Floquet theory combined with both a low energy description and full tight-binding models, we clarify the selection rules, the quasienergy band structure, as well as their connection with the two-terminal and multiterminal conductance in a device setup as relevant for experiments. We show that the well-known dynamical gaps that appear in the Floquet spectrum at ±ℏΩ/2 lead to a switch-off of the quantum Hall edge transport for different edge terminations except for the armchair one, where two terms cancel out exactly. More interestingly, we show that near the Dirac point changing the laser polarization (circular right or circular left) controls the Hall conductance, by allowing to switch it on or off, or even by flipping its sign, thereby reversing the chirality of the edge states. This might lead to new avenues to fully control topologically protected transport. | |
Giustino, Feliciano; Bibes, Manuel; Lee, Jin Hong; Trier, Felix; Valentí, Roser; Winter, Stephen M; Son, Young-Woo; Taillefer, Louis; Heil, Christoph; Figueroa, Adriana I; Plaçais, Bernard; Wu, QuanSheng; Yazyev, Oleg V; Bakkers, Erik P A M; Nygård, Jesper; Forn-Diaz, Pol; de Franceschi, Silvano; Foa Torres, Luis E F; McIver, James; Kumar, Anshuman; Low, Tony; Galceran, Regina; Valenzuela, Sergio; Costache, Marius Vasile; Manchon, Aurélien; Kim, Eun-Ah; Schleder, Gabriel Ravanhani; Fazzio, Adalberto; Roche, Stephan The 2021 Quantum Materials Roadmap Journal Article Open Access Journal of Physics: Materials, 3 , pp. 042006, 2021. @article{10.1088/2515-7639/abb74e, title = {The 2021 Quantum Materials Roadmap}, author = {Feliciano Giustino and Manuel Bibes and Jin Hong Lee and Felix Trier and Roser Valent\'{i} and Stephen M Winter and Young-Woo Son and Louis Taillefer and Christoph Heil and Adriana I Figueroa and Bernard Pla\c{c}ais and QuanSheng Wu and Oleg V Yazyev and Erik P A M Bakkers and Jesper Nygr{a}rd and Pol Forn-Diaz and Silvano de Franceschi and Luis E F {Foa Torres} and James McIver and Anshuman Kumar and Tony Low and Regina Galceran and Sergio Valenzuela and Marius Vasile Costache and Aur\'{e}lien Manchon and Eun-Ah Kim and Gabriel Ravanhani Schleder and Adalberto Fazzio and Stephan Roche}, url = {https://iopscience.iop.org/article/10.1088/2515-7639/abb74e}, year = {2021}, date = {2021-01-19}, journal = {Journal of Physics: Materials}, volume = {3}, pages = {042006}, abstract = {In recent years, the notion of “Quantum Materials” has emerged as a powerful unifying concept across diverse fields of science and engineering, from condensed-matter and cold-atom physics to materials science and quantum computing. Beyond traditional quantum materials such as unconventional superconductors, heavy fermions, and multiferroics, the field has significantly expanded to encompass topological quantum matter, two-dimensional materials and their van der Waals heterostructures, Moir\'{e} materials, Floquet time crystals, as well as materials and devices for quantum computation with Majorana fermions. In this Roadmap collection we aim to capture a snapshot of the most recent developments in the field, and to identify outstanding challenges and emerging opportunities. The format of the Roadmap, whereby experts in each discipline share their viewpoint and articulate their vision for quantum materials, reflects the dynamic and multifaceted nature of this research area, and is meant to encourage exchanges and discussions across traditional disciplinary boundaries. It is our hope that this collective vision will contribute to sparking new fascinating questions and activities at the intersection of materials science, condensed matter physics, device engineering, and quantum information, and to shaping a clearer landscape of quantum materials science as a new frontier of interdisciplinary scientific inquiry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In recent years, the notion of “Quantum Materials” has emerged as a powerful unifying concept across diverse fields of science and engineering, from condensed-matter and cold-atom physics to materials science and quantum computing. Beyond traditional quantum materials such as unconventional superconductors, heavy fermions, and multiferroics, the field has significantly expanded to encompass topological quantum matter, two-dimensional materials and their van der Waals heterostructures, Moiré materials, Floquet time crystals, as well as materials and devices for quantum computation with Majorana fermions. In this Roadmap collection we aim to capture a snapshot of the most recent developments in the field, and to identify outstanding challenges and emerging opportunities. The format of the Roadmap, whereby experts in each discipline share their viewpoint and articulate their vision for quantum materials, reflects the dynamic and multifaceted nature of this research area, and is meant to encourage exchanges and discussions across traditional disciplinary boundaries. It is our hope that this collective vision will contribute to sparking new fascinating questions and activities at the intersection of materials science, condensed matter physics, device engineering, and quantum information, and to shaping a clearer landscape of quantum materials science as a new frontier of interdisciplinary scientific inquiry. | |
2020 | |
Foa Torres, L E F Digging into the 3D Quantum Hall Effect [Viewpoint] Journal Article Physics, 13 , pp. 170, 2020. @article{foa_torres_3dQHE, title = {Digging into the 3D Quantum Hall Effect [Viewpoint]}, author = {L E F {Foa Torres}}, url = {https://physics.aps.org/articles/pdf/10.1103/Physics.13.170}, doi = {10.1103/Physics.13.170 }, year = {2020}, date = {2020-11-09}, journal = {Physics}, volume = {13}, pages = {170}, abstract = {Theorists invoke electron-phonon interactions to explain the recent observation of the quantum Hall effect in a 3D electronic system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Theorists invoke electron-phonon interactions to explain the recent observation of the quantum Hall effect in a 3D electronic system. | |
Aguilera, Esteban; Jaeschke-Ubiergo, R; Vidal-Silva, N; Foa Torres, Luis E F; Nunez, A S Topological magnonics in the two-dimensional van der Waals magnet CrI3 Journal Article Physical Review B, 102 (2), pp. 024409, 2020, ISSN: 2469-9950. @article{ISI:000545539000011, title = {Topological magnonics in the two-dimensional van der Waals magnet CrI3}, author = {Esteban Aguilera and R Jaeschke-Ubiergo and N Vidal-Silva and Luis E F {Foa Torres} and A S Nunez}, url = {https://arxiv.org/abs/2002.05266}, doi = {10.1103/PhysRevB.102.024409}, issn = {2469-9950}, year = {2020}, date = {2020-07-01}, journal = {Physical Review B}, volume = {102}, number = {2}, pages = {024409}, abstract = {We report on the magnon spectrum of Kitaev-Heisenberg magnets and extract the parameters to model a two-dimensional CrI3. Our minimal spin Hamiltonian includes a contribution stemming from a Heisenberg, isotropic exchange, and a contribution arising from a Kitaev interaction, anisotropic and frustrated exchange. Our calculations reveal a gap that opens at the K and K' points and the topological nature of the magnons which lead to the thermal Hall effect. Furthermore, we calculate the magnon spectrum of nanoribbons illustrating the corresponding edge states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on the magnon spectrum of Kitaev-Heisenberg magnets and extract the parameters to model a two-dimensional CrI3. Our minimal spin Hamiltonian includes a contribution stemming from a Heisenberg, isotropic exchange, and a contribution arising from a Kitaev interaction, anisotropic and frustrated exchange. Our calculations reveal a gap that opens at the K and K' points and the topological nature of the magnons which lead to the thermal Hall effect. Furthermore, we calculate the magnon spectrum of nanoribbons illustrating the corresponding edge states. | |
Calvo, Hernan L; Vargas, Jose Barrios E; Foa Torres, Luis E F Floquet boundary states in AB-stacked graphite Journal Article Physical Review B, 101 (7), pp. 075424, 2020, ISSN: 2469-9950. @article{ISI:000514315800004, title = {Floquet boundary states in AB-stacked graphite}, author = {Hernan L Calvo and Jose E Barrios Vargas and Luis E F {Foa Torres}}, url = {https://arxiv.org/abs/1911.02144}, doi = {10.1103/PhysRevB.101.075424}, issn = {2469-9950}, year = {2020}, date = {2020-02-01}, journal = {Physical Review B}, volume = {101}, number = {7}, pages = {075424}, abstract = {We report on the effect of laser illumination with circularly polarized light on the electronic structure of AB-stacked graphite samples. By using Floquet theory in combination with Green's function techniques, we find that the polarized light induces band-gap openings at the Floquet zone edge h Omega/2, bridged by chiral boundary states. These states propagate mainly along the borders of the constituting layers as evidenced by the time-averaged local density of states and the probability current density in several geometries. Semianalytic calculations of the Chern number suggest that these states are of topological nature, similar to those found in illuminated 2D samples like monolayer and bilayer graphene. These states are promising candidates for the realization of a three-dimensional version of the quantum Hall effect for Floquet systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on the effect of laser illumination with circularly polarized light on the electronic structure of AB-stacked graphite samples. By using Floquet theory in combination with Green's function techniques, we find that the polarized light induces band-gap openings at the Floquet zone edge h Omega/2, bridged by chiral boundary states. These states propagate mainly along the borders of the constituting layers as evidenced by the time-averaged local density of states and the probability current density in several geometries. Semianalytic calculations of the Chern number suggest that these states are of topological nature, similar to those found in illuminated 2D samples like monolayer and bilayer graphene. These states are promising candidates for the realization of a three-dimensional version of the quantum Hall effect for Floquet systems. | |
Cáceres-Aravena, G; Foa Torres, L E F; Vicencio, R A Topological and flat-band states induced by hybridized linear interactions in one-dimensional photonic lattices Journal Article Physical Review A, 102 (2), pp. 023505, 2020. @article{caceres-aravena_topological_2020, title = {Topological and flat-band states induced by hybridized linear interactions in one-dimensional photonic lattices}, author = { G. C\'{a}ceres-Aravena and L. E. F. {Foa Torres} and R. A. Vicencio}, url = {https://arxiv.org/abs/2004.11932}, doi = {10.1103/PhysRevA.102.023505}, year = {2020}, date = {2020-01-01}, urldate = {2020-08-08}, journal = {Physical Review A}, volume = {102}, number = {2}, pages = {023505}, abstract = {We report on a study of a one-dimensional linear photonic lattice hosting, simultaneously, fundamental and dipolar modes at every site. We show how, thanks to the coupling between different orbital modes, this minimal model exhibits rich transport and topological properties. By varying the detuning coefficient we find a regime where bands become flatter (with reduced transport) and a second regime, where both bands connect at a gap-closing transition (with enhanced transport). We detect an asymmetric transport due to the asymmetric intermode coupling and a linear energy exchange mechanism between modes. Further analysis shows that the bands have a topological transition with a nontrivial Zak phase which leads to the appearance of edge states in a finite system. Finally, for zero detuning, we found a symmetric condition for coupling constants, where the linear spectrum becomes completely flat, with states fully localized in space occupying only two lattice sites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on a study of a one-dimensional linear photonic lattice hosting, simultaneously, fundamental and dipolar modes at every site. We show how, thanks to the coupling between different orbital modes, this minimal model exhibits rich transport and topological properties. By varying the detuning coefficient we find a regime where bands become flatter (with reduced transport) and a second regime, where both bands connect at a gap-closing transition (with enhanced transport). We detect an asymmetric transport due to the asymmetric intermode coupling and a linear energy exchange mechanism between modes. Further analysis shows that the bands have a topological transition with a nontrivial Zak phase which leads to the appearance of edge states in a finite system. Finally, for zero detuning, we found a symmetric condition for coupling constants, where the linear spectrum becomes completely flat, with states fully localized in space occupying only two lattice sites. | |
Foa Torres, L E F; Roche, S; Charlier, J -C Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport (second edition) Book Cambridge University Press, 2020, ISBN: 9781108476997. BibTeX | Links: @book{foa_torres_introduction_2020, title = {Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport (second edition)}, author = {L E F {Foa Torres} and S Roche and J -C Charlier}, url = {https://www.cambridge.org/us/academic/subjects/physics/condensed-matter-physics-nanoscience-and-mesoscopic-physics/introduction-graphene-based-nanomaterials-electronic-structure-quantum-transport-2nd-edition?format=HB&isbn=9781108476997}, isbn = {9781108476997}, year = {2020}, date = {2020-01-01}, urldate = {2020-06-25}, publisher = {Cambridge University Press}, keywords = {}, pubstate = {published}, tppubtype = {book} } |  |
2019 | |
Rodriguez-Mena, Esteban A; Foa Torres, L E F Topological signatures in quantum transport in anomalous Floquet-Anderson insulators Journal Article Physical Review B, 100 (19), pp. 195429, 2019, ISSN: 2469-9950. @article{ISI:000498851300011, title = {Topological signatures in quantum transport in anomalous Floquet-Anderson insulators}, author = {Esteban A Rodriguez-Mena and L E F {Foa Torres}}, url = {https://arxiv.org/abs/1909.05957}, doi = {10.1103/PhysRevB.100.195429}, issn = {2469-9950}, year = {2019}, date = {2019-11-01}, journal = {Physical Review B}, volume = {100}, number = {19}, pages = {195429}, abstract = {Topological states require the presence of extended bulk states, as usually found in the picture of energy bands and topological states bridging the bulk gaps. But in driven systems this can be circumvented, and one can get topological states coexisting with fully localized bulk states, as in the case of the anomalous Floquet-Anderson insulator. Here, we show the fingerprints of this peculiar topological phase in the transport properties and their dependence on the disorder strength, geometrical configuration (two-terminal and multiterminal setups), and details of the driving protocol.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Topological states require the presence of extended bulk states, as usually found in the picture of energy bands and topological states bridging the bulk gaps. But in driven systems this can be circumvented, and one can get topological states coexisting with fully localized bulk states, as in the case of the anomalous Floquet-Anderson insulator. Here, we show the fingerprints of this peculiar topological phase in the transport properties and their dependence on the disorder strength, geometrical configuration (two-terminal and multiterminal setups), and details of the driving protocol. | |
Foa Torres, Luis E F A sudden twist Journal Article Nature Physics, 15 (10), pp. 988-989, 2019, ISSN: 1745-2473. BibTeX | Links: @article{ISI:000488590700009, title = {A sudden twist}, author = {Luis E F {Foa Torres}}, url = {https://rdcu.be/bJgEY}, doi = {10.1038/s41567-019-0595-4}, issn = {1745-2473}, year = {2019}, date = {2019-10-01}, journal = {Nature Physics}, volume = {15}, number = {10}, pages = {988-989}, keywords = {}, pubstate = {published}, tppubtype = {article} } | |
Foa Torres, Luis E F Perspective on topological states of non-Hermitian lattices Journal Article Highly cited Journal of Physics: Materials, 3 (1), pp. 014002, 2019, ISSN: 2515-7639, (Invited article for Focus Issue on Topological Matter). @article{torres_perspective_2019, title = {Perspective on topological states of non-Hermitian lattices}, author = {Luis E F {Foa Torres}}, url = {https://doi.org/10.1088%2F2515-7639%2Fab4092}, doi = {10.1088/2515-7639/ab4092}, issn = {2515-7639}, year = {2019}, date = {2019-01-01}, urldate = {2020-08-08}, journal = {Journal of Physics: Materials}, volume = {3}, number = {1}, pages = {014002}, abstract = {The search of topological states in non-Hermitian systems has gained a strong momentum over the last two years climbing to the level of an emergent research front. In this perspective we give an overview with a focus on connecting this topic to others like Floquet systems. Furthermore, using a simple scattering picture we discuss an interpretation of concepts like the Hamiltonian’s defectiveness, i.e. the lack of a full basis of eigenstates, crucial in many discussions of topological phases of non-Hermitian Hamiltonians.}, note = {Invited article for Focus Issue on Topological Matter}, keywords = {}, pubstate = {published}, tppubtype = {article} } The search of topological states in non-Hermitian systems has gained a strong momentum over the last two years climbing to the level of an emergent research front. In this perspective we give an overview with a focus on connecting this topic to others like Floquet systems. Furthermore, using a simple scattering picture we discuss an interpretation of concepts like the Hamiltonian’s defectiveness, i.e. the lack of a full basis of eigenstates, crucial in many discussions of topological phases of non-Hermitian Hamiltonians. | |
Bajpai, U; Popescu, B S; Plecháč, P; Nikolić, B K; Foa Torres, L E F; Ishizuka, H; Nagaosa, N Spatio-temporal dynamics of shift current quantum pumping by femtosecond light pulse Journal Article Open Access Journal of Physics: Materials, 2 (2), pp. 025004, 2019, ISSN: 2515-7639. @article{bajpai_spatio-temporal_2019, title = {Spatio-temporal dynamics of shift current quantum pumping by femtosecond light pulse}, author = {U Bajpai and B S Popescu and P Plech\'{a}\v{c} and B K Nikoli\'{c} and L E F {Foa Torres} and H Ishizuka and N Nagaosa}, url = {https://arxiv.org/abs/1803.04404}, doi = {10.1088/2515-7639/ab0a3e}, issn = {2515-7639}, year = {2019}, date = {2019-01-01}, urldate = {2020-08-08}, journal = {Journal of Physics: Materials}, volume = {2}, number = {2}, pages = {025004}, abstract = {Shift current\textemdasha photocurrent induced by light irradiating noncentrosymmetric materials in the absence of any bias voltage or built-in electric field\textemdashis one of the mechanisms of the so-called bulk photovoltaic effect. It has been traditionally described as a nonlinear optical response of a periodic solid to continuous wave light using a perturbative formula, which is linear in the intensity of light and which involves Berry connection describing the shift in the center of mass position of the Wannier wave function associated with the transition between the valence and conduction bands of the solid. Since shift current is solely due to off-diagonal elements of the nonequilibrium density matrix that encode quantum correlations, its peculiar space\textendashtime dynamics in response to femtosecond light pulse employed locally can be expected. To study such response requires to analyze realistic two-terminal devices, instead of traditional periodic solids, for which we choose paradigmatic Rice\textendashMele model sandwiched between two metallic electrodes and apply to it time-dependent nonequilibrium Green function algorithms scaling linearly in the number of time steps and capable of treating nonperturbative effects in the amplitude of external time-dependent fields. This reveals novel features: superballistic transport, signified by time dependence of the displacement of the photoexcited charge carriers from the spot where the femtosecond light pulse is applied toward the electrodes; and photocurrent quadratic in light intensity at subgap frequencies of light due to two-photon absorption processes that were missed in previous perturbative analyses. Furthermore, frequency dependence of the DC component of the photocurrent reveals shift current as a realization of nonadiabatic quantum charge pumping enabled by breaking of left\textendashright symmetry of the device structure. This demonstrates that a much wider class of systems, than the usually considered polar noncentrosymmetric bulk materials, can be exploited to generate nonzero DC component of photocurrent in response to unpolarized light and optimize shift-current-based solar cells and optoelectronic devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Shift current—a photocurrent induced by light irradiating noncentrosymmetric materials in the absence of any bias voltage or built-in electric field—is one of the mechanisms of the so-called bulk photovoltaic effect. It has been traditionally described as a nonlinear optical response of a periodic solid to continuous wave light using a perturbative formula, which is linear in the intensity of light and which involves Berry connection describing the shift in the center of mass position of the Wannier wave function associated with the transition between the valence and conduction bands of the solid. Since shift current is solely due to off-diagonal elements of the nonequilibrium density matrix that encode quantum correlations, its peculiar space–time dynamics in response to femtosecond light pulse employed locally can be expected. To study such response requires to analyze realistic two-terminal devices, instead of traditional periodic solids, for which we choose paradigmatic Rice–Mele model sandwiched between two metallic electrodes and apply to it time-dependent nonequilibrium Green function algorithms scaling linearly in the number of time steps and capable of treating nonperturbative effects in the amplitude of external time-dependent fields. This reveals novel features: superballistic transport, signified by time dependence of the displacement of the photoexcited charge carriers from the spot where the femtosecond light pulse is applied toward the electrodes; and photocurrent quadratic in light intensity at subgap frequencies of light due to two-photon absorption processes that were missed in previous perturbative analyses. Furthermore, frequency dependence of the DC component of the photocurrent reveals shift current as a realization of nonadiabatic quantum charge pumping enabled by breaking of left–right symmetry of the device structure. This demonstrates that a much wider class of systems, than the usually considered polar noncentrosymmetric bulk materials, can be exploited to generate nonzero DC component of photocurrent in response to unpolarized light and optimize shift-current-based solar cells and optoelectronic devices. | |
2018 | |
Berdakin, M; Vargas, Barrios J E; Foa Torres, L E F Directional control of charge and valley currents in a graphene-based device Journal Article Physical Chemistry Chemical Physics, 20 (45), pp. 28720-28725, 2018, ISSN: 1463-9076. @article{ISI:000451089900033, title = {Directional control of charge and valley currents in a graphene-based device}, author = {M Berdakin and J E Barrios Vargas and L E F {Foa Torres}}, url = {https://chemrxiv.org/engage/chemrxiv/article-details/60c73f3f337d6cce34e264e7}, doi = {10.1039/c8cp04878a}, issn = {1463-9076}, year = {2018}, date = {2018-12-01}, journal = {Physical Chemistry Chemical Physics}, volume = {20}, number = {45}, pages = {28720-28725}, abstract = {We propose a directional switching effect in a metallic device. To this end we exploit a graphene-based device with a three-terminal geometry in the presence of a magnetic field. We show that unidirectional charge and valley currents can be controlled by the Fermi energy and the magnetic field direction in the active device. Interestingly, unidirectional transport of charges and valleys is generated between two-terminals at the same bias voltage. Furthermore, we quantify the valley depolarization as a function of disorder concentration. Our results open a way for active graphene-based valleytronics devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose a directional switching effect in a metallic device. To this end we exploit a graphene-based device with a three-terminal geometry in the presence of a magnetic field. We show that unidirectional charge and valley currents can be controlled by the Fermi energy and the magnetic field direction in the active device. Interestingly, unidirectional transport of charges and valleys is generated between two-terminals at the same bias voltage. Furthermore, we quantify the valley depolarization as a function of disorder concentration. Our results open a way for active graphene-based valleytronics devices. | |
Martinez Alvarez, V M; Barrios Vargas, J E; Berdakin, M; Foa Torres, L E F Topological states of non-Hermitian systems Journal Article Highly cited European Physical Journal-Special Topics, 227 (12), pp. 1295-1308, 2018, ISSN: 1951-6355, (Invited short review for the special issue “Topological States of Matter: Theory and Applications”). @article{ISI:000455553900002, title = {Topological states of non-Hermitian systems}, author = {V M {Martinez Alvarez} and J E {Barrios Vargas} and M Berdakin and L E F {Foa Torres}}, url = {https://repositorio.uchile.cl/bitstream/handle/2250/169477/Topological_states.pdf?sequence=1&isAllowed=y}, doi = {10.1140/epjst/e2018-800091-5}, issn = {1951-6355}, year = {2018}, date = {2018-12-01}, journal = {European Physical Journal-Special Topics}, volume = {227}, number = {12}, pages = {1295-1308}, abstract = {Recently, the search for topological states of matter has turned to non-Hermitian systems, which exhibit a rich variety of unique properties without Hermitian counterparts. Lattices modeled through non-Hermitian Hamiltonians appear in the context of photonic systems, where one needs to account for gain and loss, circuits of resonators, and also when modeling the lifetime due to interactions in condensed matter systems. Here we provide a brief overview of this rapidly growing subject, the search for topological states and a bulk-boundary correspondence in non-Hermitian systems.}, note = {Invited short review for the special issue “Topological States of Matter: Theory and Applications”}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recently, the search for topological states of matter has turned to non-Hermitian systems, which exhibit a rich variety of unique properties without Hermitian counterparts. Lattices modeled through non-Hermitian Hamiltonians appear in the context of photonic systems, where one needs to account for gain and loss, circuits of resonators, and also when modeling the lifetime due to interactions in condensed matter systems. Here we provide a brief overview of this rapidly growing subject, the search for topological states and a bulk-boundary correspondence in non-Hermitian systems. | |
Calvo, Hernan L; Luna, Javier S; Dal Lago, Virginia ; Foa Torres, Luis E F Robust edge states induced by electron-phonon interaction in graphene nanoribbons Journal Article Physical Review B, 98 (3), pp. 035423, 2018, ISSN: 2469-9950. @article{ISI:000438855600002, title = {Robust edge states induced by electron-phonon interaction in graphene nanoribbons}, author = {Hernan L Calvo and Javier S Luna and Virginia {Dal Lago} and Luis E F {Foa Torres}}, url = {https://arxiv.org/abs/1805.00576}, doi = {10.1103/PhysRevB.98.035423}, issn = {2469-9950}, year = {2018}, date = {2018-07-01}, journal = {Physical Review B}, volume = {98}, number = {3}, pages = {035423}, abstract = {The search of new means of generating and controlling topological states of matter is at the front of many joint efforts, including band-gap engineering by doping and light-induced topological states. Most of our understading, however, is based on a single particle picture. Topological states in systems including interaction effects, such as electron-electron and electron-phonon, remain less explored. By exploiting a nonperturbative and nonadiabatic picture, here we show how the interaction between electrons and a coherent phonon mode can lead to a band gap hosting edge states of topological origin. Further numerical simulations witness the robustness of these states against different types of disorder. Our results contribute to the search of topological states, in this case in a minimal Fock space.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The search of new means of generating and controlling topological states of matter is at the front of many joint efforts, including band-gap engineering by doping and light-induced topological states. Most of our understading, however, is based on a single particle picture. Topological states in systems including interaction effects, such as electron-electron and electron-phonon, remain less explored. By exploiting a nonperturbative and nonadiabatic picture, here we show how the interaction between electrons and a coherent phonon mode can lead to a band gap hosting edge states of topological origin. Further numerical simulations witness the robustness of these states against different types of disorder. Our results contribute to the search of topological states, in this case in a minimal Fock space. | |
Chesta Lopez, J; Foa Torres, L E F; Nunez, A S Multiterminal conductance at the surface of a Weyl semimetal Journal Article Physical Review B, 97 (12), pp. 125419, 2018, ISSN: 2469-9950. @article{ISI:000427638900007, title = {Multiterminal conductance at the surface of a Weyl semimetal}, author = {J {Chesta Lopez} and L E F {Foa Torres} and A S Nunez}, url = {https://repositorio.uchile.cl/bitstream/handle/2250/155800/item_85043982183.pdf?sequence=1&isAllowed=y}, doi = {10.1103/PhysRevB.97.125419}, issn = {2469-9950}, year = {2018}, date = {2018-03-01}, journal = {Physical Review B}, volume = {97}, number = {12}, pages = {125419}, abstract = {Weyl semimetals are a new paradigmatic topological phase of matter featuring a gapless spectrum. One of its most distinctive features is the presence of Fermi arc surface states. Here, we report on atomistic simulations of the dc conductance and quantum Hall response of a minimalWeyl semimetal. By using scattering theory we show that a quantized Hall conductance with a nonvanishing longitudinal conductance emerges associated to the Fermi arc surface states with a remarkable robustness to high concentrations of defects in the system. Additionally, we predict that a slab of a Weyl semimetal with broken time-reversal symmetry bears persistent currents fully determined by the system size and the lattice parameters.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Weyl semimetals are a new paradigmatic topological phase of matter featuring a gapless spectrum. One of its most distinctive features is the presence of Fermi arc surface states. Here, we report on atomistic simulations of the dc conductance and quantum Hall response of a minimalWeyl semimetal. By using scattering theory we show that a quantized Hall conductance with a nonvanishing longitudinal conductance emerges associated to the Fermi arc surface states with a remarkable robustness to high concentrations of defects in the system. Additionally, we predict that a slab of a Weyl semimetal with broken time-reversal symmetry bears persistent currents fully determined by the system size and the lattice parameters. | |
Martinez Alvarez, V M; Barrios Vargas, J E; Foa Torres, L E F Non-Hermitian robust edge states in one dimension: Anomalous localization and eigenspace condensation at exceptional points Journal Article Highly cited Physical Review B, 97 (12), pp. 121401, 2018, ISSN: 2469-9950. @article{ISI:000426779100002, title = {Non-Hermitian robust edge states in one dimension: Anomalous localization and eigenspace condensation at exceptional points}, author = {V M {Martinez Alvarez} and J E {Barrios Vargas} and L E F {Foa Torres}}, url = {https://repositorio.uchile.cl/bitstream/handle/2250/169335/Non_hermitian.pdf?sequence=1&isAllowed=y}, doi = {10.1103/PhysRevB.97.121401}, issn = {2469-9950}, year = {2018}, date = {2018-03-01}, journal = {Physical Review B}, volume = {97}, number = {12}, pages = {121401}, abstract = {Capital to topological insulators, the bulk-boundary correspondence ties a topological invariant computed from the bulk (extended) states with those at the boundary, which are hence robust to disorder. Here we put forward a different ordering unique to non-Hermitian lattices whereby a pristine system becomes devoid of extended states, a property which turns out to be robust to disorder. This is enabled by a peculiar type of non-Hermitian degeneracy where a macroscopic fraction of the states coalesce at a single point with a geometrical multiplicity of 1.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Capital to topological insulators, the bulk-boundary correspondence ties a topological invariant computed from the bulk (extended) states with those at the boundary, which are hence robust to disorder. Here we put forward a different ordering unique to non-Hermitian lattices whereby a pristine system becomes devoid of extended states, a property which turns out to be robust to disorder. This is enabled by a peculiar type of non-Hermitian degeneracy where a macroscopic fraction of the states coalesce at a single point with a geometrical multiplicity of 1. | |
2017 | |
Dal Lago, V; Morell, Suarez E; Foa Torres, L E F One-way transport in laser-illuminated bilayer graphene: A Floquet isolator Journal Article Physical Review B, 96 (23), pp. 235409, 2017, ISSN: 2469-9950. @article{ISI:000417487200003, title = {One-way transport in laser-illuminated bilayer graphene: A Floquet isolator}, author = {V {Dal Lago} and E Suarez Morell and L E F {Foa Torres}}, url = {https://repositorio.uchile.cl/bitstream/handle/2250/168735/One-way-transport.pdf?sequence=1&isAllowed=y}, doi = {10.1103/PhysRevB.96.235409}, issn = {2469-9950}, year = {2017}, date = {2017-12-01}, journal = {Physical Review B}, volume = {96}, number = {23}, pages = {235409}, abstract = {We explore the Floquet band structure and electronic transport in laser-illuminated bilayer graphene ribbons. By using a bias voltage perpendicular to the graphene bilayer we show how to get one-way charge and valley transport among two unbiased leads. In contrast to quantum pumping, our proposal uses a different mechanism based on generating a nonreciprocal band structure with a built-in directionality. The Floquet states at one edge of a graphene layer become hybridized with the continuum on the other layer, so the resulting band structure allows for one-way transport as in an isolator. Our proof of concept may serve as a building block for devices exploiting one-way states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We explore the Floquet band structure and electronic transport in laser-illuminated bilayer graphene ribbons. By using a bias voltage perpendicular to the graphene bilayer we show how to get one-way charge and valley transport among two unbiased leads. In contrast to quantum pumping, our proposal uses a different mechanism based on generating a nonreciprocal band structure with a built-in directionality. The Floquet states at one edge of a graphene layer become hybridized with the continuum on the other layer, so the resulting band structure allows for one-way transport as in an isolator. Our proof of concept may serve as a building block for devices exploiting one-way states. | |
Kalugin, Nikolai G; Jing, Lei; Morell, Eric Suarez; Dyer, Gregory C; Wickey, Lee; Ovezmyradov, Mekan; Grine, Albert D; Wanke, Michael C; Shaner, Eric A; Lau, Chun Ning; Torres, Luis Foa E F; Fistul, Mikhail V; Efetov, Konstantin B Photoelectric polarization-sensitive broadband photoresponse from interface junction states in graphene Journal Article 2D Materials, 4 (1), 2017, ISSN: 2053-1583. @article{ISI:000387051100002, title = {Photoelectric polarization-sensitive broadband photoresponse from interface junction states in graphene}, author = {Nikolai G Kalugin and Lei Jing and Eric Suarez Morell and Gregory C Dyer and Lee Wickey and Mekan Ovezmyradov and Albert D Grine and Michael C Wanke and Eric A Shaner and Chun Ning Lau and Luis E F Foa Torres and Mikhail V Fistul and Konstantin B Efetov}, doi = {10.1088/2053-1583/4/1/015002}, issn = {2053-1583}, year = {2017}, date = {2017-03-01}, journal = {2D Materials}, volume = {4}, number = {1}, abstract = {Graphene has established itself as a promising optoelectronic material. Many details of the photoresponse (PR) mechanisms in graphene in the THz-to-visible range have been revealed, however, new intricacies continue to emerge. Interface junctions, formed at the boundaries between parts of graphene with different number of layers or different stacking orders, and making connection between electrical contacts, provide another peculiar setup to establish PR. Here, we experimentally demonstrate an enhanced polarization sensitive photoelectric PR in graphene sheets containing interface junctions as compared to homogenous graphene sheets in the visible, infrared, and THz spectral regions. Our numerical simulations show that highly localized electronic states are created at the interface junctions, and these states exhibit a unique energy spectrum and enhanced probabilities for optical transitions. The interaction of electrons from interface junction states with electromagnetic fields generates a polarization-sensitive PR that is maximal for the polarization direction perpendicular to the junction interface.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Graphene has established itself as a promising optoelectronic material. Many details of the photoresponse (PR) mechanisms in graphene in the THz-to-visible range have been revealed, however, new intricacies continue to emerge. Interface junctions, formed at the boundaries between parts of graphene with different number of layers or different stacking orders, and making connection between electrical contacts, provide another peculiar setup to establish PR. Here, we experimentally demonstrate an enhanced polarization sensitive photoelectric PR in graphene sheets containing interface junctions as compared to homogenous graphene sheets in the visible, infrared, and THz spectral regions. Our numerical simulations show that highly localized electronic states are created at the interface junctions, and these states exhibit a unique energy spectrum and enhanced probabilities for optical transitions. The interaction of electrons from interface junction states with electromagnetic fields generates a polarization-sensitive PR that is maximal for the polarization direction perpendicular to the junction interface. | |
2016 | |
Ingaramo, L H; Foa Torres, L E F Valley filtering by a line-defect in graphene: quantum interference and inversion of the filter effect Journal Article Journal of Physics-Condensed Matter, 28 (48), pp. 485302, 2016, ISSN: 0953-8984. @article{ISI:000385676900001, title = {Valley filtering by a line-defect in graphene: quantum interference and inversion of the filter effect}, author = {L H Ingaramo and L E F {Foa Torres}}, url = {https://arxiv.org/abs/1609.05769}, doi = {10.1088/0953-8984/28/48/485302}, issn = {0953-8984}, year = {2016}, date = {2016-12-01}, journal = {Journal of Physics-Condensed Matter}, volume = {28}, number = {48}, pages = {485302}, abstract = {Valley filters are crucial to any device exploiting the valley degree of freedom. By using an atomistic model, we analyze the mechanism leading to the valley filtering produced by a line-defect in graphene and show how it can be inverted by external means. Thanks to a mode decomposition applied to a tight-binding model we can resolve the different transport channels in k-space while keeping a simple but accurate description of the band structure, both close and further away from the Dirac point. This allows the understanding of a destructive interference effect, specifically a Fano resonance or antiresonance located on the p-side of the Dirac point leading to a reduced conductance. We show that in the neighborhood of this feature the valley filtering can be reversed by changing the occupations with a gate voltage, the mechanism is explained in terms of a valley-dependent Fano resonance splitting. Our results open the door for enhanced control of valley transport in graphene-based devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Valley filters are crucial to any device exploiting the valley degree of freedom. By using an atomistic model, we analyze the mechanism leading to the valley filtering produced by a line-defect in graphene and show how it can be inverted by external means. Thanks to a mode decomposition applied to a tight-binding model we can resolve the different transport channels in k-space while keeping a simple but accurate description of the band structure, both close and further away from the Dirac point. This allows the understanding of a destructive interference effect, specifically a Fano resonance or antiresonance located on the p-side of the Dirac point leading to a reduced conductance. We show that in the neighborhood of this feature the valley filtering can be reversed by changing the occupations with a gate voltage, the mechanism is explained in terms of a valley-dependent Fano resonance splitting. Our results open the door for enhanced control of valley transport in graphene-based devices. | |
Lovey, D A; Usaj, Gonzalo; Foa Torres, L E F; Balseiro, C A Floquet bound states around defects and adatoms in graphene Journal Article Physical Review B, 93 (24), pp. 245434, 2016, ISSN: 2469-9950. @article{ISI:000378816300004, title = {Floquet bound states around defects and adatoms in graphene}, author = {D A Lovey and Gonzalo Usaj and L E F {Foa Torres} and C A Balseiro}, doi = {10.1103/PhysRevB.93.245434}, issn = {2469-9950}, year = {2016}, date = {2016-06-01}, journal = {Physical Review B}, volume = {93}, number = {24}, pages = {245434}, abstract = {Recent studies have focused on laser-induced gaps in graphene which have been shown to have a topological origin, thereby hosting robust states at the sample edges. While the focus has remainedmainly on these topological chiral edge states, the Floquet bound states around defects lack a detailed study. In this paper we present such a study covering large defects of different shape and also vacancy-like defects and adatoms at the dynamical gap at h Omega/2 (h Omega being the photon energy). Our results, based on analytical calculations as well as numerics for full tight-binding models, show that the bound states are chiral and appear in a number which grows with the defect size. Furthermore, while the bound states exist regardless of the type of the defect's edge termination (zigzag, armchair, mixed), the spectrum is strongly dependent on it. In the case of top adatoms, the bound state quasienergies depend on the adatoms energy. The appearance of such bound states might open the door to the presence of topological effects on the bulk transport properties of dirty graphene.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent studies have focused on laser-induced gaps in graphene which have been shown to have a topological origin, thereby hosting robust states at the sample edges. While the focus has remainedmainly on these topological chiral edge states, the Floquet bound states around defects lack a detailed study. In this paper we present such a study covering large defects of different shape and also vacancy-like defects and adatoms at the dynamical gap at h Omega/2 (h Omega being the photon energy). Our results, based on analytical calculations as well as numerics for full tight-binding models, show that the bound states are chiral and appear in a number which grows with the defect size. Furthermore, while the bound states exist regardless of the type of the defect's edge termination (zigzag, armchair, mixed), the spectrum is strongly dependent on it. In the case of top adatoms, the bound state quasienergies depend on the adatoms energy. The appearance of such bound states might open the door to the presence of topological effects on the bulk transport properties of dirty graphene. | |
Foa Torres, L E F; Dal Lago, V; Morell, Suarez E Crafting zero-bias one-way transport of charge and spin Journal Article Physical Review B, 93 (7), pp. 075438, 2016, ISSN: 2469-9950. @article{ISI:000370841200006, title = {Crafting zero-bias one-way transport of charge and spin}, author = {L E F {Foa Torres} and V {Dal Lago} and E Suarez Morell}, url = {https://repositorio.uchile.cl/bitstream/handle/2250/139102/Crafting-zero-bias-one-way-transport-of-charge-and-spin.pdf?sequence=1&isAllowed=y}, doi = {10.1103/PhysRevB.93.075438}, issn = {2469-9950}, year = {2016}, date = {2016-02-01}, journal = {Physical Review B}, volume = {93}, number = {7}, pages = {075438}, abstract = {We explore the electronic structure and transport properties of a metal on top of a (weakly coupled) two-dimensional topological insulator. Unlike the widely studied junctions between topological nontrivial Materials, the systems studied here allow for a unique band structure and transport steering. First, states on the topological insulator layer may coexist with the gapless bulk and, second, the edge states on one edge can be selectively switched off, thereby leading to nearly perfect directional transport of charge and spin even in the zero bias limit. We illustrate these phenomena for Bernal stacked bilayer graphene with Haldane or intrinsic spin-orbit terms and a perpendicular bias voltage. This opens a path for realizing directed transport in Materials such as van der Waals heterostructures, monolayer, and ultrathin topological insulators.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We explore the electronic structure and transport properties of a metal on top of a (weakly coupled) two-dimensional topological insulator. Unlike the widely studied junctions between topological nontrivial Materials, the systems studied here allow for a unique band structure and transport steering. First, states on the topological insulator layer may coexist with the gapless bulk and, second, the edge states on one edge can be selectively switched off, thereby leading to nearly perfect directional transport of charge and spin even in the zero bias limit. We illustrate these phenomena for Bernal stacked bilayer graphene with Haldane or intrinsic spin-orbit terms and a perpendicular bias voltage. This opens a path for realizing directed transport in Materials such as van der Waals heterostructures, monolayer, and ultrathin topological insulators. | |
2015 | |
Dal Lago, V; Atala, M; Foa Torres, L E F Floquet topological transitions in a driven one-dimensional topological insulator Journal Article Physical Review A, 92 (2), pp. 023624, 2015, ISSN: 1050-2947. @article{ISI:000359672200007, title = {Floquet topological transitions in a driven one-dimensional topological insulator}, author = {V {Dal Lago} and M Atala and L E F {Foa Torres}}, doi = {10.1103/PhysRevA.92.023624}, issn = {1050-2947}, year = {2015}, date = {2015-08-01}, journal = {Physical Review A}, volume = {92}, number = {2}, pages = {023624}, abstract = {The Su-Schrieffer-Heeger model of polyacetylene is a paradigmatic Hamiltonian exhibiting nontrivial edge states. By using Floquet theory we study how the spectrum of this one-dimensional topological insulator is affected by a time-dependent potential. In particular, we provide evidence of the competition among different photon-assisted processes and the native topology of the unperturbed Hamiltonian to settle the resulting topology at different driving frequencies. While some regions of the quasienergy spectrum develop new gaps hosting Floquet edge states, the native gap can be dramatically reduced and the original edge states may be destroyed or replaced by new Floquet edge states. Our study is complemented by an analysis of the Zak phase applied to the Floquet bands. Besides serving as a simple example for understanding the physics of driven topological phases, our results could find a promising testing ground in cold-matter experiments.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Su-Schrieffer-Heeger model of polyacetylene is a paradigmatic Hamiltonian exhibiting nontrivial edge states. By using Floquet theory we study how the spectrum of this one-dimensional topological insulator is affected by a time-dependent potential. In particular, we provide evidence of the competition among different photon-assisted processes and the native topology of the unperturbed Hamiltonian to settle the resulting topology at different driving frequencies. While some regions of the quasienergy spectrum develop new gaps hosting Floquet edge states, the native gap can be dramatically reduced and the original edge states may be destroyed or replaced by new Floquet edge states. Our study is complemented by an analysis of the Zak phase applied to the Floquet bands. Besides serving as a simple example for understanding the physics of driven topological phases, our results could find a promising testing ground in cold-matter experiments. | |
Calvo, H L; Foa Torres, L E F; Perez-Piskunow, P M; Balseiro, C A; Usaj, Gonzalo Floquet interface states in illuminated three-dimensional topological insulators Journal Article Physical Review B, 91 (24), pp. 241404, 2015, ISSN: 2469-9950. @article{ISI:000356129800001, title = {Floquet interface states in illuminated three-dimensional topological insulators}, author = {H L Calvo and L E F {Foa Torres} and P M Perez-Piskunow and C A Balseiro and Gonzalo Usaj}, doi = {10.1103/PhysRevB.91.241404}, issn = {2469-9950}, year = {2015}, date = {2015-06-01}, journal = {Physical Review B}, volume = {91}, number = {24}, pages = {241404}, abstract = {Recent experiments showed that the surface of a three-dimensional topological insulator develops gaps in the Floquet-Bloch band spectrum when illuminated with a circularly polarized laser. These Floquet-Bloch bands are characterized by nontrivial Chern numbers which only depend on the helicity of the polarization of the radiation field. Here we propose a setup consisting of a pair of counterrotating lasers, and show that one-dimensional chiral states emerge at the interface between the two lasers. These interface states turn out to be spin polarized and may trigger interesting applications in the field of optoelectronics and spintronics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent experiments showed that the surface of a three-dimensional topological insulator develops gaps in the Floquet-Bloch band spectrum when illuminated with a circularly polarized laser. These Floquet-Bloch bands are characterized by nontrivial Chern numbers which only depend on the helicity of the polarization of the radiation field. Here we propose a setup consisting of a pair of counterrotating lasers, and show that one-dimensional chiral states emerge at the interface between the two lasers. These interface states turn out to be spin polarized and may trigger interesting applications in the field of optoelectronics and spintronics. | |
Perez-Piskunow, P M; Foa Torres, L E F; Usaj, Gonzalo Hierarchy of Floquet gaps and edge states for driven honeycomb lattices Journal Article Physical Review A, 91 (4), pp. 043625, 2015, ISSN: 1050-2947. @article{ISI:000353121400005, title = {Hierarchy of Floquet gaps and edge states for driven honeycomb lattices}, author = {P M Perez-Piskunow and L E F {Foa Torres} and Gonzalo Usaj}, doi = {10.1103/PhysRevA.91.043625}, issn = {1050-2947}, year = {2015}, date = {2015-04-01}, journal = {Physical Review A}, volume = {91}, number = {4}, pages = {043625}, abstract = {Electromagnetic driving in a honeycomb lattice can induce gaps and topological edge states with a structure of increasing complexity as the frequency of the driving lowers. While the high-frequency case is the most simple to analyze we focus on the multiple photon processes allowed in the low-frequency regime to unveil the hierarchy of Floquet edge states. In the case of low intensities an analytical approach allows us to derive effective Hamiltonians and address the topological character of each gap in a constructive manner. At high intensities we obtain the net number of edge states, given by the winding number, with a numerical calculation of the Chern numbers of each Floquet band. Using these methods, we find a hierarchy that resembles that of a Russian nesting doll. This hierarchy classifies the gaps and the associated edge states in different orders according to the electron-photon coupling strength. For large driving intensities, we rely on the numerical calculation of the winding number, illustrated in a map of topological phase transitions. The hierarchy unveiled with the low-energy effective Hamiltonians, along with the map of topological phase transitions, discloses the complexity of the Floquet band structure in the low-frequency regime. The proposed method for obtaining the effective Hamiltonian can be easily adapted to other Dirac Hamiltonians of two-dimensional Materials and even the surface of a three-dimensional topological insulator.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electromagnetic driving in a honeycomb lattice can induce gaps and topological edge states with a structure of increasing complexity as the frequency of the driving lowers. While the high-frequency case is the most simple to analyze we focus on the multiple photon processes allowed in the low-frequency regime to unveil the hierarchy of Floquet edge states. In the case of low intensities an analytical approach allows us to derive effective Hamiltonians and address the topological character of each gap in a constructive manner. At high intensities we obtain the net number of edge states, given by the winding number, with a numerical calculation of the Chern numbers of each Floquet band. Using these methods, we find a hierarchy that resembles that of a Russian nesting doll. This hierarchy classifies the gaps and the associated edge states in different orders according to the electron-photon coupling strength. For large driving intensities, we rely on the numerical calculation of the winding number, illustrated in a map of topological phase transitions. The hierarchy unveiled with the low-energy effective Hamiltonians, along with the map of topological phase transitions, discloses the complexity of the Floquet band structure in the low-frequency regime. The proposed method for obtaining the effective Hamiltonian can be easily adapted to other Dirac Hamiltonians of two-dimensional Materials and even the surface of a three-dimensional topological insulator. | |
Dal Lago, V; Foa Torres, L E F Line defects and quantum Hall plateaus in graphene Journal Article Journal of Physics-Condensed Matter, 27 (14), pp. 145303, 2015, ISSN: 0953-8984. @article{ISI:000351738400005, title = {Line defects and quantum Hall plateaus in graphene}, author = {V {Dal Lago} and L E F {Foa Torres}}, doi = {10.1088/0953-8984/27/14/145303}, issn = {0953-8984}, year = {2015}, date = {2015-04-01}, journal = {Journal of Physics-Condensed Matter}, volume = {27}, number = {14}, pages = {145303}, abstract = {Line defects in graphene can be either tailored-growth or arise naturally and are at the center of many discussions. Here we study the multiterminal conductance of graphene with an extended line defect in the quantum Hall regime analyzing the effects of the geometry of the setup, disorder and strain on the quantum Hall plateaus. We show that the defect turns out to affect the local and non-local conductance in very different ways depending on the geometrical configuration. When the defect is parallel to the sample edges one gets an equivalent circuit formed by parallel resistors. In contrast, when the defect bridges opposite edges, the Hall conductance may remain unaltered depending on the geometry of the voltage/current probes. The role of disorder, strain and the microscopic details of the defect in our results is also discussed. We show that the defect provides a realization of the electrical analog of an optical beam splitter. Its peculiar energy dependent inter-edge transmission allows it to be turned on or off at will and it may be used for routing the chiral edge states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Line defects in graphene can be either tailored-growth or arise naturally and are at the center of many discussions. Here we study the multiterminal conductance of graphene with an extended line defect in the quantum Hall regime analyzing the effects of the geometry of the setup, disorder and strain on the quantum Hall plateaus. We show that the defect turns out to affect the local and non-local conductance in very different ways depending on the geometrical configuration. When the defect is parallel to the sample edges one gets an equivalent circuit formed by parallel resistors. In contrast, when the defect bridges opposite edges, the Hall conductance may remain unaltered depending on the geometry of the voltage/current probes. The role of disorder, strain and the microscopic details of the defect in our results is also discussed. We show that the defect provides a realization of the electrical analog of an optical beam splitter. Its peculiar energy dependent inter-edge transmission allows it to be turned on or off at will and it may be used for routing the chiral edge states. | |
2014 | |
Foa Torres, L E F; Perez-Piskunow, P M; Balseiro, C A; Usaj, Gonzalo Multiterminal Conductance of a Floquet Topological Insulator Journal Article Physical Review Letters, 113 (26), pp. 266801, 2014, ISSN: 0031-9007. @article{ISI:000346836900008, title = {Multiterminal Conductance of a Floquet Topological Insulator}, author = {L E F {Foa Torres} and P M Perez-Piskunow and C A Balseiro and Gonzalo Usaj}, url = {https://ri.conicet.gov.ar/bitstream/handle/11336/31800/CONICET_Digital_Nro.d43d95e3-2abd-4a55-a56b-8a48ac31e686_A.pdf?sequence=2&isAllowed=y}, doi = {10.1103/PhysRevLett.113.266801}, issn = {0031-9007}, year = {2014}, date = {2014-12-01}, journal = {Physical Review Letters}, volume = {113}, number = {26}, pages = {266801}, abstract = {We report on simulations of the dc conductance and quantum Hall response of a Floquet topological insulator using Floquet scattering theory. Our results reveal that laser-induced edge states lead to quantum Hall plateaus once imperfect matching with the nonilluminated leads is lessened. The magnitude of the Hall plateaus, however, is not directly related to the number and chirality of all the edge states at a given energy, as usual. Instead, the plateaus are dominated by those edge states adding to the time-averaged density of states. Therefore, the dc quantum Hall conductance of a Floquet topological insulator is not directly linked to topological invariants of the full Floquet bands.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on simulations of the dc conductance and quantum Hall response of a Floquet topological insulator using Floquet scattering theory. Our results reveal that laser-induced edge states lead to quantum Hall plateaus once imperfect matching with the nonilluminated leads is lessened. The magnitude of the Hall plateaus, however, is not directly related to the number and chirality of all the edge states at a given energy, as usual. Instead, the plateaus are dominated by those edge states adding to the time-averaged density of states. Therefore, the dc quantum Hall conductance of a Floquet topological insulator is not directly linked to topological invariants of the full Floquet bands. | |
Usaj, Gonzalo; Perez-Piskunow, P M; Foa Torres, L E F; Balseiro, C A Irradiated graphene as a tunable Floquet topological insulator Journal Article Highly cited Physical Review B, 90 (11), pp. 115423, 2014, ISSN: 1098-0121. @article{ISI:000342159000003, title = {Irradiated graphene as a tunable Floquet topological insulator}, author = {Gonzalo Usaj and P M Perez-Piskunow and L E F {Foa Torres} and C A Balseiro}, url = {https://ri.conicet.gov.ar/bitstream/handle/11336/31852/CONICET_Digital_Nro.27f6decb-79ac-482b-bed6-a1656c3987a9_A.pdf?sequence=2&isAllowed=y}, doi = {10.1103/PhysRevB.90.115423}, issn = {1098-0121}, year = {2014}, date = {2014-09-01}, journal = {Physical Review B}, volume = {90}, number = {11}, pages = {115423}, abstract = {In the presence of a circularly polarized mid-infrared radiation graphene develops dynamical band gaps in its quasienergy band structure and becomes a Floquet insulator. Here, we analyze how topologically protected edge states arise inside these gaps in the presence of an edge. Our results show that the gap appearing at h Omega/2, where h Omega is the photon energy, is bridged by two chiral edge states whose propagation direction is set by the direction of the polarization of the radiation field. Therefore, both the propagation direction and the energy window where the states appear can be controlled externally. We present both analytical and numerical calculations that fully characterize these states. This is complemented by simple topological arguments that account for them and by numerical calculations for the case of the semi-infinite sample, thereby eliminating finite-size effects.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the presence of a circularly polarized mid-infrared radiation graphene develops dynamical band gaps in its quasienergy band structure and becomes a Floquet insulator. Here, we analyze how topologically protected edge states arise inside these gaps in the presence of an edge. Our results show that the gap appearing at h Omega/2, where h Omega is the photon energy, is bridged by two chiral edge states whose propagation direction is set by the direction of the polarization of the radiation field. Therefore, both the propagation direction and the energy window where the states appear can be controlled externally. We present both analytical and numerical calculations that fully characterize these states. This is complemented by simple topological arguments that account for them and by numerical calculations for the case of the semi-infinite sample, thereby eliminating finite-size effects. | |
Bracamonte, M V; Lacconi, G I; Urreta, S E; Foa Torres, L E F On the Nature of Defects in Liquid-Phase Exfoliated Graphene Journal Article Journal of Physical Chemistry C, 118 (28), pp. 15455-15459, 2014, ISSN: 1932-7447. @article{ISI:000339368700041, title = {On the Nature of Defects in Liquid-Phase Exfoliated Graphene}, author = {M V Bracamonte and G I Lacconi and S E Urreta and L E F {Foa Torres}}, doi = {10.1021/jp501930a}, issn = {1932-7447}, year = {2014}, date = {2014-07-01}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {28}, pages = {15455-15459}, abstract = {Liquid-phase exfoliation is one of the most promising routes for large-scale production of multilayer graphene dispersions. These dispersions, which may be used in coatings, composites, or paints, are believed to contain disorder-free graphene multilayers. Here, we address the nature of defects in such samples obtained by liquid-phase exfoliation of graphite powder in N-methyl-2-pyrrolidone. Our Raman spectroscopy data challenge the assumption that these multilayers are free of bulk defects, revealing that defect localization strongly depends on the sonication time. For short ultrasound times, defects are located mainly at the layer edges but they turn out to build up in the bulk for ultrasonic times above 2 h. This knowledge may help to devise better strategies to achieve high-quality graphene dispersions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Liquid-phase exfoliation is one of the most promising routes for large-scale production of multilayer graphene dispersions. These dispersions, which may be used in coatings, composites, or paints, are believed to contain disorder-free graphene multilayers. Here, we address the nature of defects in such samples obtained by liquid-phase exfoliation of graphite powder in N-methyl-2-pyrrolidone. Our Raman spectroscopy data challenge the assumption that these multilayers are free of bulk defects, revealing that defect localization strongly depends on the sonication time. For short ultrasound times, defects are located mainly at the layer edges but they turn out to build up in the bulk for ultrasonic times above 2 h. This knowledge may help to devise better strategies to achieve high-quality graphene dispersions. | |
Ramos, J P; Foa Torres, L E F; Orellana, P A; Apel, V M Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling Journal Article Journal of Applied Physics, 115 (12), pp. 124507, 2014, ISSN: 0021-8979. @article{ISI:000333901100090, title = {Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling}, author = {J P Ramos and L E F {Foa Torres} and P A Orellana and V M Apel}, doi = {10.1063/1.4868902}, issn = {0021-8979}, year = {2014}, date = {2014-03-01}, journal = {Journal of Applied Physics}, volume = {115}, number = {12}, pages = {124507}, abstract = {We consider the generation of a pure spin-current at zero bias voltage with a single time-dependent potential. To such end we study a device made of a mesoscopic ring connected to electrodes and clarify the interplay between a magnetic flux, spin-orbit coupling, and non-adiabatic driving in the production of a spin and electrical current. By using Floquet theory, we show that the generated spin to charge current ratio can be controlled by tuning the spin-orbit coupling. (C) 2014 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We consider the generation of a pure spin-current at zero bias voltage with a single time-dependent potential. To such end we study a device made of a mesoscopic ring connected to electrodes and clarify the interplay between a magnetic flux, spin-orbit coupling, and non-adiabatic driving in the production of a spin and electrical current. By using Floquet theory, we show that the generated spin to charge current ratio can be controlled by tuning the spin-orbit coupling. (C) 2014 AIP Publishing LLC. | |
Perez-Piskunow, P M; Usaj, Gonzalo; Balseiro, C A; Torres, Foa L E F Floquet chiral edge states in graphene Journal Article Highly cited Physical Review B, 89 (12), pp. 121401, 2014, ISSN: 1098-0121. @article{ISI:000332456000001, title = {Floquet chiral edge states in graphene}, author = {P M Perez-Piskunow and Gonzalo Usaj and C A Balseiro and L E F Foa Torres}, url = {https://ri.conicet.gov.ar/bitstream/handle/11336/27548/CONICET_Digital_Nro.ad91487c-974f-44c4-a660-13f320b80798_A.pdf?sequence=2&isAllowed=y}, doi = {10.1103/PhysRevB.89.121401}, issn = {1098-0121}, year = {2014}, date = {2014-03-01}, journal = {Physical Review B}, volume = {89}, number = {12}, pages = {121401}, abstract = {We report on the emergence of laser-induced chiral edge states in graphene ribbons. Insights on the nature of these Floquet states is provided by an analytical solution which is complemented with numerical simulations of the transport properties. Guided by these results we show that graphene can be used for realizing nonequilibrium topological states with striking tunability: while the laser intensity can be used to control their velocity and decay length, changing the laser polarization switches their propagation direction.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on the emergence of laser-induced chiral edge states in graphene ribbons. Insights on the nature of these Floquet states is provided by an analytical solution which is complemented with numerical simulations of the transport properties. Guided by these results we show that graphene can be used for realizing nonequilibrium topological states with striking tunability: while the laser intensity can be used to control their velocity and decay length, changing the laser polarization switches their propagation direction. | |
Foa Torres, L E F; Roche, S; Charlier, J C Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport Book Cambridge University Press, 2014, ISBN: 9781107030831. BibTeX | Links: @book{foa_torres_introduction_2014, title = {Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport}, author = {L E F {Foa Torres} and S Roche and J C Charlier}, url = {http://www.cambridge.org/9781107030831}, isbn = {9781107030831}, year = {2014}, date = {2014-01-01}, publisher = {Cambridge University Press}, keywords = {}, pubstate = {published}, tppubtype = {book} } |  |
2013 | |
Ingaramo, Lucas H; Foa Torres, Luis E F Quantum charge pumping in graphene-based devices: When lattice defects do help Journal Article Applied Physics Letters, 103 (12), pp. 123508, 2013, ISSN: 0003-6951. @article{ISI:000324826000083, title = {Quantum charge pumping in graphene-based devices: When lattice defects do help}, author = {Lucas H Ingaramo and Luis E F {Foa Torres}}, doi = {10.1063/1.4821262}, issn = {0003-6951}, year = {2013}, date = {2013-09-01}, journal = {Applied Physics Letters}, volume = {103}, number = {12}, pages = {123508}, abstract = {Quantum charge pumping, the quantum coherent generation of a dc current at zero bias through time-dependent potentials, provides outstanding opportunities for metrology and the development of nanodevices. The long electronic coherence times and high quality of the crystal structure of graphene may provide suitable building blocks for such quantum pumps. Here, we focus in adiabatic quantum pumping through graphene nanoribbons in the Fabry-Perot regime highlighting the crucial role of defects by using atomistic simulations. We show that even a single defect added to the pristine structure may produce a two orders of magnitude increase in the pumped charge. (C) 2013 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Quantum charge pumping, the quantum coherent generation of a dc current at zero bias through time-dependent potentials, provides outstanding opportunities for metrology and the development of nanodevices. The long electronic coherence times and high quality of the crystal structure of graphene may provide suitable building blocks for such quantum pumps. Here, we focus in adiabatic quantum pumping through graphene nanoribbons in the Fabry-Perot regime highlighting the crucial role of defects by using atomistic simulations. We show that even a single defect added to the pristine structure may produce a two orders of magnitude increase in the pumped charge. (C) 2013 AIP Publishing LLC. | |
Calvo, Hernan L; Perez-Piskunow, Pablo M; Pastawski, Horacio M; Roche, Stephan; Foa Torres, Luis E F Non-perturbative effects of laser illumination on the electrical properties of graphene nanoribbons Journal Article Journal of Physics-Condensed Matter, 25 (14), pp. 144202, 2013, ISSN: 0953-8984, (Invited Article). @article{ISI:000316210200005, title = {Non-perturbative effects of laser illumination on the electrical properties of graphene nanoribbons}, author = {Hernan L Calvo and Pablo M Perez-Piskunow and Horacio M Pastawski and Stephan Roche and Luis E F {Foa Torres}}, doi = {10.1088/0953-8984/25/14/144202}, issn = {0953-8984}, year = {2013}, date = {2013-04-01}, journal = {Journal of Physics-Condensed Matter}, volume = {25}, number = {14}, pages = {144202}, abstract = {Floquet theory combined with a realistic description of the electronic structure of illuminated graphene and graphene nanoribbons is developed to assess the emergent non-adiabatic and non-perturbative effects on the electronic properties. Here we introduce an efficient computational scheme and illustrate its use by applying it to graphene nanoribbons in the presence of both linear and circular polarization. The interplay between confinement due to the finite sample size and laser-induced transitions is shown to lead to sharp features in the average conductance and density of states. Particular emphasis is given to the emergence of the bulk limit response.}, note = {Invited Article}, keywords = {}, pubstate = {published}, tppubtype = {article} } Floquet theory combined with a realistic description of the electronic structure of illuminated graphene and graphene nanoribbons is developed to assess the emergent non-adiabatic and non-perturbative effects on the electronic properties. Here we introduce an efficient computational scheme and illustrate its use by applying it to graphene nanoribbons in the presence of both linear and circular polarization. The interplay between confinement due to the finite sample size and laser-induced transitions is shown to lead to sharp features in the average conductance and density of states. Particular emphasis is given to the emergence of the bulk limit response. | |
Calvo, Hernán L; Pastawski, Horacio M; Roche, Stephan; Torres, Foa On the Possibility of Observing Tunable Laser-Induced Bandgaps in Graphene Book Chapter Graphene, Carbon Nanotubes, and Nanostructures, 2013. @inbook{calvo_possibility_2013, title = {On the Possibility of Observing Tunable Laser-Induced Bandgaps in Graphene}, author = {Hern\'{a}n L Calvo and Horacio M Pastawski and Stephan Roche and Foa Torres}, url = {https://www.taylorfrancis.com/}, doi = {10.1201/b13905-3}, year = {2013}, date = {2013-01-01}, urldate = {2020-08-08}, booktitle = {Graphene, Carbon Nanotubes, and Nanostructures}, abstract = {This chapter focuses on the interplay between optical and electronic properties, and addresses the issue of tunability of the latter using a laser field.}, keywords = {}, pubstate = {published}, tppubtype = {inbook} } This chapter focuses on the interplay between optical and electronic properties, and addresses the issue of tunability of the latter using a laser field. | |
2012 | |
Calvo, Hernan L; Perez-Piskunow, Pablo M; Roche, Stephan; Torres, Luis Foa E F Laser-induced effects on the electronic features of graphene nanoribbons Journal Article Applied Physics Letters, 101 (25), pp. 123508, 2012, ISSN: 0003-6951. @article{ISI:000312780000098, title = {Laser-induced effects on the electronic features of graphene nanoribbons}, author = {Hernan L Calvo and Pablo M Perez-Piskunow and Stephan Roche and Luis E F Foa Torres}, doi = {10.1063/1.4772496}, issn = {0003-6951}, year = {2012}, date = {2012-12-01}, journal = {Applied Physics Letters}, volume = {101}, number = {25}, pages = {123508}, abstract = {We study the interplay between lateral confinement and photon-induced processes on the electronic properties of illuminated graphene nanoribbons. We find that by tuning the device setup (edges geometries, ribbon width, and polarization direction), a laser with frequency Omega may either not affect the electronic structure, or induce bandgaps or depletions at +/-(h) over bar Omega=2, and/or at other energies not commensurate with half the photon energy. Similar features are also observed in the dc conductance, suggesting the use of the polarization direction to switch on and off the graphene device. Our results could guide the design of novel types of optoelectronic nano-devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772496]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the interplay between lateral confinement and photon-induced processes on the electronic properties of illuminated graphene nanoribbons. We find that by tuning the device setup (edges geometries, ribbon width, and polarization direction), a laser with frequency Omega may either not affect the electronic structure, or induce bandgaps or depletions at +/-(h) over bar Omega=2, and/or at other energies not commensurate with half the photon energy. Similar features are also observed in the dc conductance, suggesting the use of the polarization direction to switch on and off the graphene device. Our results could guide the design of novel types of optoelectronic nano-devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772496] | |
Morell, Eric Suarez; Foa Torres, Luis E F Radiation effects on the electronic properties of bilayer graphene Journal Article Physical Review B, 86 (12), pp. 125449, 2012, ISSN: 2469-9950. @article{ISI:000309268500009, title = {Radiation effects on the electronic properties of bilayer graphene}, author = {Eric Suarez Morell and Luis E F {Foa Torres}}, doi = {10.1103/PhysRevB.86.125449}, issn = {2469-9950}, year = {2012}, date = {2012-09-01}, journal = {Physical Review B}, volume = {86}, number = {12}, pages = {125449}, abstract = {We report on the effects of laser illumination on the electronic properties of bilayer graphene. By using Floquet theory combined with Green's functions, we unveil the appearance of laser-induced gaps not only at integer multiples of h Omega/2 but also at the Dirac point with features which are shown to depend strongly on the laser polarization. Trigonal warping corrections are shown to lead to important corrections for radiation in the terahertz range, reducing the size of the dynamical gaps. Furthermore, our analysis of the topological properties at low energies reveals that, when irradiated with linearly polarized light, ideal bilayer graphene behaves as a trivial insulator, whereas circular polarization leads to a nontrivial insulator per valley.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on the effects of laser illumination on the electronic properties of bilayer graphene. By using Floquet theory combined with Green's functions, we unveil the appearance of laser-induced gaps not only at integer multiples of h Omega/2 but also at the Dirac point with features which are shown to depend strongly on the laser polarization. Trigonal warping corrections are shown to lead to important corrections for radiation in the terahertz range, reducing the size of the dynamical gaps. Furthermore, our analysis of the topological properties at low energies reveals that, when irradiated with linearly polarized light, ideal bilayer graphene behaves as a trivial insulator, whereas circular polarization leads to a nontrivial insulator per valley. | |
2011 | |
Foa Torres, Luis E F; Calvo, Hernan L; Rocha, Claudia G; Cuniberti, Gianaurelio Enhancing single-parameter quantum charge pumping in carbon-based devices Journal Article Applied Physics Letters, 99 (9), 2011, ISSN: 0003-6951. @article{ISI:000294489300027, title = {Enhancing single-parameter quantum charge pumping in carbon-based devices}, author = {Luis E F {Foa Torres} and Hernan L Calvo and Claudia G Rocha and Gianaurelio Cuniberti}, doi = {10.1063/1.3630025}, issn = {0003-6951}, year = {2011}, date = {2011-08-01}, journal = {Applied Physics Letters}, volume = {99}, number = {9}, abstract = {We present a theoretical study of quantum charge pumping with a single ac gate applied to graphene nanoribbons and carbon nanotubes operating with low resistance contacts. By combining Floquet theory with Green's function formalism, we show that the pumped current can be tuned and enhanced by up to two orders of magnitude by an appropriate choice of device length, gate voltage intensity, and driving frequency and amplitude. These results offer a promising alternative for enhancing the pumped currents in these carbon-based devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3630025]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a theoretical study of quantum charge pumping with a single ac gate applied to graphene nanoribbons and carbon nanotubes operating with low resistance contacts. By combining Floquet theory with Green's function formalism, we show that the pumped current can be tuned and enhanced by up to two orders of magnitude by an appropriate choice of device length, gate voltage intensity, and driving frequency and amplitude. These results offer a promising alternative for enhancing the pumped currents in these carbon-based devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3630025] | |
Calvo, Hernan L; Pastawski, Horacio M; Roche, Stephan; Torres, Luis Foa E F Tuning laser-induced band gaps in graphene Journal Article Applied Physics Letters, 98 (23), pp. 092102, 2011, ISSN: 0003-6951. @article{ISI:000291658900028, title = {Tuning laser-induced band gaps in graphene}, author = {Hernan L Calvo and Horacio M Pastawski and Stephan Roche and Luis E F Foa Torres}, url = {https://arxiv.org/abs/1105.2327}, doi = {10.1063/1.3597412}, issn = {0003-6951}, year = {2011}, date = {2011-06-01}, journal = {Applied Physics Letters}, volume = {98}, number = {23}, pages = {092102}, abstract = {Could a laser field lead to the much sought-after tunable band gaps in graphene? By using Floquet theory combined with Green's functions techniques, we predict that a laser field in the mid-infrared range can produce observable band gaps in the electronic structure of graphene. Furthermore, we show how they can be tuned by using the laser polarization. Our results could serve as a guidance to design optoelectronic nanodevices. (c) 2011 American Institute of Physics. [doi:10.1063/1.3597412]}, keywords = {}, pubstate = {published}, tppubtype = {article} } Could a laser field lead to the much sought-after tunable band gaps in graphene? By using Floquet theory combined with Green's functions techniques, we predict that a laser field in the mid-infrared range can produce observable band gaps in the electronic structure of graphene. Furthermore, we show how they can be tuned by using the laser polarization. Our results could serve as a guidance to design optoelectronic nanodevices. (c) 2011 American Institute of Physics. [doi:10.1063/1.3597412] | |
Rocha, C G; Pacheco, M; Foa Torres, L E F; Cuniberti, G; Latge, A Transport response of carbon-based resonant cavities under time-dependent potential and magnetic fields Journal Article EPL, 94 (4), pp. 47002, 2011, ISSN: 0295-5075. @article{ISI:000290718900020, title = {Transport response of carbon-based resonant cavities under time-dependent potential and magnetic fields}, author = {C G Rocha and M Pacheco and L E F {Foa Torres} and G Cuniberti and A Latge}, doi = {10.1209/0295-5075/94/47002}, issn = {0295-5075}, year = {2011}, date = {2011-05-01}, journal = {EPL}, volume = {94}, number = {4}, pages = {47002}, abstract = {Here we report theoretical transport calculations on carbon-based nanoMaterials used as resonator cavities under the effects of a time-dependent field. A magnetic field is considered as an extra modulator tool, able to encode binary ON or OFF transmission states on the quantum systems. Regular either complex conductance Fabry-Perot patterns mapped onto gate vs. bias voltage diagrams can be revealed depending on the set of parameters used on the simulations (amplitude and frequency of the ac field and magnetic-field intensity). We discuss the interplay between the effects on the resonant cavity conductance, caused by the presence of an ac gate plate, which tends to delocalize the electronic wave functions, and an external magnetic field that oppositely localizes the electrons. Copyright (C) EPLA, 2011}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here we report theoretical transport calculations on carbon-based nanoMaterials used as resonator cavities under the effects of a time-dependent field. A magnetic field is considered as an extra modulator tool, able to encode binary ON or OFF transmission states on the quantum systems. Regular either complex conductance Fabry-Perot patterns mapped onto gate vs. bias voltage diagrams can be revealed depending on the set of parameters used on the simulations (amplitude and frequency of the ac field and magnetic-field intensity). We discuss the interplay between the effects on the resonant cavity conductance, caused by the presence of an ac gate plate, which tends to delocalize the electronic wave functions, and an external magnetic field that oppositely localizes the electrons. Copyright (C) EPLA, 2011 | |
2010 | |
Poetschke, M; Rocha, C G; Foa Torres, L E F; Roche, S; Cuniberti, G Modeling graphene-based nanoelectromechanical devices Journal Article Physical Review B, 81 (19), pp. 115435, 2010, ISSN: 2469-9950. @article{ISI:000278142000014, title = {Modeling graphene-based nanoelectromechanical devices}, author = {M Poetschke and C G Rocha and L E F {Foa Torres} and S Roche and G Cuniberti}, doi = {10.1103/PhysRevB.81.193404}, issn = {2469-9950}, year = {2010}, date = {2010-05-01}, journal = {Physical Review B}, volume = {81}, number = {19}, pages = {115435}, abstract = {We report on a theoretical study of charge transport properties of graphene nanoribbons under external mechanical stress. The influence of mechanical forces on the ribbon conductance is shown to be strongly dependent on the ribbon edge symmetry, i.e., zigzag versus armchair. In contrast to zigzag-edge nanoribbons which remain robust against high strain deformations, a stretching-induced metal-semiconductor transition is obtained for armchair-edge configurations. Our results point out that armchair edge ribbons are consequently much better suited for electromechanical applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on a theoretical study of charge transport properties of graphene nanoribbons under external mechanical stress. The influence of mechanical forces on the ribbon conductance is shown to be strongly dependent on the ribbon edge symmetry, i.e., zigzag versus armchair. In contrast to zigzag-edge nanoribbons which remain robust against high strain deformations, a stretching-induced metal-semiconductor transition is obtained for armchair-edge configurations. Our results point out that armchair edge ribbons are consequently much better suited for electromechanical applications. | |
Rocha, Claudia G; Foa Torres, Luis E F; Cuniberti, Gianaurelio ac transport in graphene-based Fabry-Peacuterot devices Journal Article Physical Review B, 81 (11), pp. 115435, 2010, ISSN: 2469-9950. @article{ISI:000276248800148, title = {ac transport in graphene-based Fabry-Peacuterot devices}, author = {Claudia G Rocha and Luis E F {Foa Torres} and Gianaurelio Cuniberti}, doi = {10.1103/PhysRevB.81.115435}, issn = {2469-9950}, year = {2010}, date = {2010-03-01}, journal = {Physical Review B}, volume = {81}, number = {11}, pages = {115435}, abstract = {We report on a theoretical study of the effects of time-dependent fields on electronic transport through graphene nanoribbon devices. The Fabry-Peacuterot interference pattern is modified by an ac gating in a way that depends strongly on the shape of the graphene edges. While for armchair edges the patterns are found to be regular and can be controlled very efficiently by tuning the ac field, samples with zigzag edges exhibit a much more complex interference pattern due to their peculiar electronic structure. These studies highlight the main role played by geometric details of graphene nanoribbons within the coherent transport regime. We also extend our analysis to noise power response identifying under which conditions it is possible to minimize the current fluctuations as well as exploring scaling properties of noise with the length and width of the systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on a theoretical study of the effects of time-dependent fields on electronic transport through graphene nanoribbon devices. The Fabry-Peacuterot interference pattern is modified by an ac gating in a way that depends strongly on the shape of the graphene edges. While for armchair edges the patterns are found to be regular and can be controlled very efficiently by tuning the ac field, samples with zigzag edges exhibit a much more complex interference pattern due to their peculiar electronic structure. These studies highlight the main role played by geometric details of graphene nanoribbons within the coherent transport regime. We also extend our analysis to noise power response identifying under which conditions it is possible to minimize the current fluctuations as well as exploring scaling properties of noise with the length and width of the systems. | |
2009 | |
Foa Torres, Luis E F; Cuniberti, G Controlling the conductance and noise of driven carbon-based Fabry-Perot devices Journal Article Applied Physics Letters, 94 (22), pp. 222103, 2009, ISSN: 0003-6951. @article{ISI:000266674300026, title = {Controlling the conductance and noise of driven carbon-based Fabry-Perot devices}, author = {Luis E F {Foa Torres} and G Cuniberti}, doi = {10.1063/1.3147865}, issn = {0003-6951}, year = {2009}, date = {2009-06-01}, journal = {Applied Physics Letters}, volume = {94}, number = {22}, pages = {222103}, abstract = {We report on ac transport through carbon nanotube Fabry-Perot devices. We show that tuning the intensity of the ac gating induces an alternation of suppression and partial revival of the conductance interference pattern. For frequencies matching integer multiples of the level spacing of the system Delta, the conductance remains irresponsive to the external field. In contrast, the noise in the low bias voltage limit behaves as in the static case only when the frequency matches an even multiple of the level spacing, thereby highlighting its phase sensitivity in a manifestation of the wagon-wheel effect in the quantum domain.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on ac transport through carbon nanotube Fabry-Perot devices. We show that tuning the intensity of the ac gating induces an alternation of suppression and partial revival of the conductance interference pattern. For frequencies matching integer multiples of the level spacing of the system Delta, the conductance remains irresponsive to the external field. In contrast, the noise in the low bias voltage limit behaves as in the static case only when the frequency matches an even multiple of the level spacing, thereby highlighting its phase sensitivity in a manifestation of the wagon-wheel effect in the quantum domain. | |
Foa Torres, L E F; Cuniberti, G AC transport in carbon-based devices: challenges and perspectives Journal Article COMPTES RENDUS PHYSIQUE, 10 (4), pp. 297-304, 2009, ISSN: 1631-0705. @article{ISI:000268471600005, title = {AC transport in carbon-based devices: challenges and perspectives}, author = {L E F {Foa Torres} and G Cuniberti}, doi = {10.1016/j.crhy.2009.05.003}, issn = {1631-0705}, year = {2009}, date = {2009-05-01}, journal = {COMPTES RENDUS PHYSIQUE}, volume = {10}, number = {4}, pages = {297-304}, abstract = {Time-dependent fields are a valuable tool to control fundamental quantum phenomena in highly coherent low dimensional electron systems. Carbon nanotubes and graphene are a promising ground for these studies. Here we offer a brief overview of driven electronic transport in carbon-based Materials with the main focus on carbon nanotubes. Recent results predicting control of the current and noise in nanotube based Fabry-Perot devices are highlighted. To cite this article: LEX Foa Torres, G. Cuniberti, C. R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Time-dependent fields are a valuable tool to control fundamental quantum phenomena in highly coherent low dimensional electron systems. Carbon nanotubes and graphene are a promising ground for these studies. Here we offer a brief overview of driven electronic transport in carbon-based Materials with the main focus on carbon nanotubes. Recent results predicting control of the current and noise in nanotube based Fabry-Perot devices are highlighted. To cite this article: LEX Foa Torres, G. Cuniberti, C. R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved. | |
2008 | |
Foa Torres, Luis E F; Avriller, Remi; Roche, Stephan Nonequilibrium energy gaps in carbon nanotubes: Role of phonon symmetries Journal Article Physical Review B, 78 (3), pp. 035412, 2008, ISSN: 2469-9950. @article{ISI:000258190300128, title = {Nonequilibrium energy gaps in carbon nanotubes: Role of phonon symmetries}, author = {Luis E F {Foa Torres} and Remi Avriller and Stephan Roche}, doi = {10.1103/PhysRevB.78.035412}, issn = {2469-9950}, year = {2008}, date = {2008-07-01}, journal = {Physical Review B}, volume = {78}, number = {3}, pages = {035412}, abstract = {We report on a theoretical study of inelastic backscattering processes and quantum transport in metallic carbon nanotubes. The consequences of a Peierls-like mechanism due to e-ph interaction with optic phonons in the transport properties is explored. The occurrence of nonequilibrium energy gaps driven by an applied bias voltage is derived from a nonperturbative treatment of electron-phonon coupling with longitudinal optic as well as K A(1)' modes. The case of armchair tubes is explicitly considered, and further generalizations to tubes of arbitrary helicity are outlined.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report on a theoretical study of inelastic backscattering processes and quantum transport in metallic carbon nanotubes. The consequences of a Peierls-like mechanism due to e-ph interaction with optic phonons in the transport properties is explored. The occurrence of nonequilibrium energy gaps driven by an applied bias voltage is derived from a nonperturbative treatment of electron-phonon coupling with longitudinal optic as well as K A(1)' modes. The case of armchair tubes is explicitly considered, and further generalizations to tubes of arbitrary helicity are outlined. | |
2022 | |
Experimental observation of edge states in SSH-Stub photonic lattices Journal Article Open Access Physical Review Research, 4 (013185), 2022. | |
Copropagating edge states produced by the interaction between electrons and chiral phonons in two-dimensional materials Journal Article Physical Review Letters, 128 , pp. 066801, 2022. | |
Robustness of spin-polarized edge states in a two-dimensional topological semimetal without inversion symmetry Journal Article Physical Review B, 105 , pp. 075403, 2022. | |
2021 | |
A valley of opportunities Journal Article Physics World, 11 , pp. 43, 2021, ISSN: 2058-7058. | |
Quadrature protection of squeezed states in a one-dimensional topological insulator Journal Article Open Access Quantum, 5 , pp. 526, 2021. | |
Spin-polarized tunable photocurrents Journal Article Nano Letters, 21 , pp. 3177, 2021. | |
Quantum Hall edge states under periodic driving: A Floquet induced chirality switch Journal Article Open Access Physical Review Research, 3 , pp. 013201, 2021. | |
The 2021 Quantum Materials Roadmap Journal Article Open Access Journal of Physics: Materials, 3 , pp. 042006, 2021. | |
2020 | |
Digging into the 3D Quantum Hall Effect [Viewpoint] Journal Article Physics, 13 , pp. 170, 2020. | |
Topological magnonics in the two-dimensional van der Waals magnet CrI3 Journal Article Physical Review B, 102 (2), pp. 024409, 2020, ISSN: 2469-9950. | |
Floquet boundary states in AB-stacked graphite Journal Article Physical Review B, 101 (7), pp. 075424, 2020, ISSN: 2469-9950. | |
Topological and flat-band states induced by hybridized linear interactions in one-dimensional photonic lattices Journal Article Physical Review A, 102 (2), pp. 023505, 2020. | |
Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport (second edition) Book Cambridge University Press, 2020, ISBN: 9781108476997. | |
2019 | |
Topological signatures in quantum transport in anomalous Floquet-Anderson insulators Journal Article Physical Review B, 100 (19), pp. 195429, 2019, ISSN: 2469-9950. | |
A sudden twist Journal Article Nature Physics, 15 (10), pp. 988-989, 2019, ISSN: 1745-2473. | |
Perspective on topological states of non-Hermitian lattices Journal Article Highly cited Journal of Physics: Materials, 3 (1), pp. 014002, 2019, ISSN: 2515-7639, (Invited article for Focus Issue on Topological Matter). | |
Spatio-temporal dynamics of shift current quantum pumping by femtosecond light pulse Journal Article Open Access Journal of Physics: Materials, 2 (2), pp. 025004, 2019, ISSN: 2515-7639. | |
2018 | |
Directional control of charge and valley currents in a graphene-based device Journal Article Physical Chemistry Chemical Physics, 20 (45), pp. 28720-28725, 2018, ISSN: 1463-9076. | |
Topological states of non-Hermitian systems Journal Article Highly cited European Physical Journal-Special Topics, 227 (12), pp. 1295-1308, 2018, ISSN: 1951-6355, (Invited short review for the special issue “Topological States of Matter: Theory and Applications”). | |
Robust edge states induced by electron-phonon interaction in graphene nanoribbons Journal Article Physical Review B, 98 (3), pp. 035423, 2018, ISSN: 2469-9950. | |
Multiterminal conductance at the surface of a Weyl semimetal Journal Article Physical Review B, 97 (12), pp. 125419, 2018, ISSN: 2469-9950. | |
Non-Hermitian robust edge states in one dimension: Anomalous localization and eigenspace condensation at exceptional points Journal Article Highly cited Physical Review B, 97 (12), pp. 121401, 2018, ISSN: 2469-9950. | |
2017 | |
One-way transport in laser-illuminated bilayer graphene: A Floquet isolator Journal Article Physical Review B, 96 (23), pp. 235409, 2017, ISSN: 2469-9950. | |
Photoelectric polarization-sensitive broadband photoresponse from interface junction states in graphene Journal Article 2D Materials, 4 (1), 2017, ISSN: 2053-1583. | |
2016 | |
Valley filtering by a line-defect in graphene: quantum interference and inversion of the filter effect Journal Article Journal of Physics-Condensed Matter, 28 (48), pp. 485302, 2016, ISSN: 0953-8984. | |
Floquet bound states around defects and adatoms in graphene Journal Article Physical Review B, 93 (24), pp. 245434, 2016, ISSN: 2469-9950. | |
Crafting zero-bias one-way transport of charge and spin Journal Article Physical Review B, 93 (7), pp. 075438, 2016, ISSN: 2469-9950. | |
2015 | |
Floquet topological transitions in a driven one-dimensional topological insulator Journal Article Physical Review A, 92 (2), pp. 023624, 2015, ISSN: 1050-2947. | |
Floquet interface states in illuminated three-dimensional topological insulators Journal Article Physical Review B, 91 (24), pp. 241404, 2015, ISSN: 2469-9950. | |
Hierarchy of Floquet gaps and edge states for driven honeycomb lattices Journal Article Physical Review A, 91 (4), pp. 043625, 2015, ISSN: 1050-2947. | |
Line defects and quantum Hall plateaus in graphene Journal Article Journal of Physics-Condensed Matter, 27 (14), pp. 145303, 2015, ISSN: 0953-8984. | |
2014 | |
Multiterminal Conductance of a Floquet Topological Insulator Journal Article Physical Review Letters, 113 (26), pp. 266801, 2014, ISSN: 0031-9007. | |
Irradiated graphene as a tunable Floquet topological insulator Journal Article Highly cited Physical Review B, 90 (11), pp. 115423, 2014, ISSN: 1098-0121. | |
On the Nature of Defects in Liquid-Phase Exfoliated Graphene Journal Article Journal of Physical Chemistry C, 118 (28), pp. 15455-15459, 2014, ISSN: 1932-7447. | |
Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling Journal Article Journal of Applied Physics, 115 (12), pp. 124507, 2014, ISSN: 0021-8979. | |
Floquet chiral edge states in graphene Journal Article Highly cited Physical Review B, 89 (12), pp. 121401, 2014, ISSN: 1098-0121. | |
Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport Book Cambridge University Press, 2014, ISBN: 9781107030831. | |
2013 | |
Quantum charge pumping in graphene-based devices: When lattice defects do help Journal Article Applied Physics Letters, 103 (12), pp. 123508, 2013, ISSN: 0003-6951. | |
Non-perturbative effects of laser illumination on the electrical properties of graphene nanoribbons Journal Article Journal of Physics-Condensed Matter, 25 (14), pp. 144202, 2013, ISSN: 0953-8984, (Invited Article). | |
On the Possibility of Observing Tunable Laser-Induced Bandgaps in Graphene Book Chapter Graphene, Carbon Nanotubes, and Nanostructures, 2013. | |
2012 | |
Laser-induced effects on the electronic features of graphene nanoribbons Journal Article Applied Physics Letters, 101 (25), pp. 123508, 2012, ISSN: 0003-6951. | |
Radiation effects on the electronic properties of bilayer graphene Journal Article Physical Review B, 86 (12), pp. 125449, 2012, ISSN: 2469-9950. | |
2011 | |
Enhancing single-parameter quantum charge pumping in carbon-based devices Journal Article Applied Physics Letters, 99 (9), 2011, ISSN: 0003-6951. | |
Tuning laser-induced band gaps in graphene Journal Article Applied Physics Letters, 98 (23), pp. 092102, 2011, ISSN: 0003-6951. | |
Transport response of carbon-based resonant cavities under time-dependent potential and magnetic fields Journal Article EPL, 94 (4), pp. 47002, 2011, ISSN: 0295-5075. | |
2010 | |
Modeling graphene-based nanoelectromechanical devices Journal Article Physical Review B, 81 (19), pp. 115435, 2010, ISSN: 2469-9950. | |
ac transport in graphene-based Fabry-Peacuterot devices Journal Article Physical Review B, 81 (11), pp. 115435, 2010, ISSN: 2469-9950. | |
2009 | |
Controlling the conductance and noise of driven carbon-based Fabry-Perot devices Journal Article Applied Physics Letters, 94 (22), pp. 222103, 2009, ISSN: 0003-6951. | |
AC transport in carbon-based devices: challenges and perspectives Journal Article COMPTES RENDUS PHYSIQUE, 10 (4), pp. 297-304, 2009, ISSN: 1631-0705. | |
2008 | |
Nonequilibrium energy gaps in carbon nanotubes: Role of phonon symmetries Journal Article Physical Review B, 78 (3), pp. 035412, 2008, ISSN: 2469-9950. | |