Docente
Ilum-CNPEM
Felipe D. C. de Lima
Publicações
2026
Lopes, Emmanuel V. C.; Sophia, Pedro H.; Lima, Felipe Crasto; Fazzio, Adalberto
Controllable Quantum Spin Hall Phases in Bi$_2$Te$_3$-Family van der Waals Heterobilayers Miscellaneous
2026.
@misc{lopes2026controllablequantumspinhall,
title = {Controllable Quantum Spin Hall Phases in Bi$_2$Te$_3$-Family van der Waals Heterobilayers},
author = {Emmanuel V. C. Lopes and Pedro H. Sophia and Felipe Crasto Lima and Adalberto Fazzio},
url = {https://arxiv.org/abs/2606.20541},
year = {2026},
date = {2026-06-18},
urldate = {2026-01-01},
abstract = {The tunability and control of topological edge/surface states are crucial for the development of new device applications. In this work, by combining first-principles calculations and Wannier-based tight-binding methods, we show the emergence of quantum spin Hall phases in van der Waals heterostructures formed by stacking two trivial quintuple layers from the BiTe family. We demonstrate the tunability of the edge states under interlayer strain and external electric field effects, suggesting the possibility of switching topological edge states on/off by external control. Additionally, the quantum spin Hall edge channels remain robust against interlayer twist, highlighting their stability against external perturbations. Our results provide a new way to create and manipulate two-dimensional topological phases in systems based on BiTe family, which can be valuable for practical applications, such as topological field effect transistors and spintronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
The tunability and control of topological edge/surface states are crucial for the development of new device applications. In this work, by combining first-principles calculations and Wannier-based tight-binding methods, we show the emergence of quantum spin Hall phases in van der Waals heterostructures formed by stacking two trivial quintuple layers from the BiTe family. We demonstrate the tunability of the edge states under interlayer strain and external electric field effects, suggesting the possibility of switching topological edge states on/off by external control. Additionally, the quantum spin Hall edge channels remain robust against interlayer twist, highlighting their stability against external perturbations. Our results provide a new way to create and manipulate two-dimensional topological phases in systems based on BiTe family, which can be valuable for practical applications, such as topological field effect transistors and spintronic devices.
Sousa, Lucas Soares; Lima, Felipe Crasto; Miwa, Roberto Hiroki
Tunable Electronic and Transport Properties of Biphenylene via Fluorination and Disorder Miscellaneous
2026.
@misc{sousa2026tunableelectronictransportproperties,
title = {Tunable Electronic and Transport Properties of Biphenylene via Fluorination and Disorder},
author = {Lucas Soares Sousa and Felipe Crasto Lima and Roberto Hiroki Miwa},
url = {https://arxiv.org/abs/2606.18083},
year = {2026},
date = {2026-06-16},
urldate = {2026-01-01},
abstract = {Biphenylene (BPN) network is a newly synthesized 2D carbon allotrope hosting anisotropic Dirac electronic states. Here, we investigate how fluorination and correlated chemical disorder modify the electronic structure and charge transport of fluorinated biphenylene (F/BPN) using density functional theory, Wannier-based tight-biding Hamiltonian, and quantum transport simulations. We show that fluorination reshapes the transport response of BPN, producing concentration-dependent anisotropic conduction regimes. For pristine and ordered fluorinated systems, we identified the emergence of negative differential resistance (NDR) and a bias-induced inversion of the preferred transport direction, from armchair to zigzag and vice versa. In contrast, disorder suppresses the NDR, driving the system toward an approximately Ohmic transport regime. At high fluorine coverage, we further observed a nonmonotonic dependence of the armchair current on adatom concentration, which we attribute to the formation of correlated quasi-linear fluor conformation that promote armchair-oriented C- transport channels while simultaneously suppressing transport along the zigzag direction. Our results demonstrate that correlated fluorination can be used as an active mechanism to engineer electronic transport.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Biphenylene (BPN) network is a newly synthesized 2D carbon allotrope hosting anisotropic Dirac electronic states. Here, we investigate how fluorination and correlated chemical disorder modify the electronic structure and charge transport of fluorinated biphenylene (F/BPN) using density functional theory, Wannier-based tight-biding Hamiltonian, and quantum transport simulations. We show that fluorination reshapes the transport response of BPN, producing concentration-dependent anisotropic conduction regimes. For pristine and ordered fluorinated systems, we identified the emergence of negative differential resistance (NDR) and a bias-induced inversion of the preferred transport direction, from armchair to zigzag and vice versa. In contrast, disorder suppresses the NDR, driving the system toward an approximately Ohmic transport regime. At high fluorine coverage, we further observed a nonmonotonic dependence of the armchair current on adatom concentration, which we attribute to the formation of correlated quasi-linear fluor conformation that promote armchair-oriented C- transport channels while simultaneously suppressing transport along the zigzag direction. Our results demonstrate that correlated fluorination can be used as an active mechanism to engineer electronic transport.
Miwa, Roberto H.; Kuritza, Danilo P.; Padilha, José E.; Freire, Rafael L. H.; Lima, Felipe Crasto; Fazzio, Adalberto
Thickness-Dependent Electronic and Transport Properties of PtSe _2 on Au(111) Journal Article
Em: J. Phys. Chem. C, 2026, ISSN: 1932-7455.
@article{Miwa2026,
title = {Thickness-Dependent Electronic and Transport Properties of PtSe _2 on Au(111)},
author = {Roberto H. Miwa and Danilo P. Kuritza and José E. Padilha and Rafael L. H. Freire and Felipe Crasto Lima and Adalberto Fazzio},
doi = {10.1021/acs.jpcc.5c07502},
issn = {1932-7455},
year = {2026},
date = {2026-04-16},
urldate = {2026-04-16},
journal = {J. Phys. Chem. C},
publisher = {American Chemical Society (ACS)},
abstract = {Among two-dimensional materials, platinum diselenide (PtSe2) has attracted interest for applications in electronic devices such as transistors and sensors, mainly due to the thickness dependence of its bandgap. Thus, understanding electronic confinement and transport properties in contact with metals is essential for device design. Here, using density functional theory, we investigated the structural, electronic, and electronic transport properties of monolayer (ML), bilayer (BL), and trilayer (TL) PtSe2 on Au(111), PtSe2-X/Au (X = ML, BL, TL). We find the emergence of a chemical interaction at the interface, leading to (i) ohmic contact, (ii) hole doping of PtSe2, and (iii) metallization of the contact layer. In PtSe2-ML/Au, the semiconductor ML becomes metallic, while in PtSe2–BL/Au and PtSe2-TL/Au, the top layers, which do not directly contact Au, become semimetallic. Transport calculations further reveal a thickness-dependent behavior of the electronic transmittance and Schottky barriers along the PtSe2-X channels in contact with the PtSe2-X/Au(111) leads. Based on this atomistic understanding, we propose a heterostructure, Au/PtSe2-TL/Au, where a metal–semiconductor transition can be tuned by mechanical strain. These results highlight the potential of few-layer PtSe2 for two-dimensional electronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Among two-dimensional materials, platinum diselenide (PtSe2) has attracted interest for applications in electronic devices such as transistors and sensors, mainly due to the thickness dependence of its bandgap. Thus, understanding electronic confinement and transport properties in contact with metals is essential for device design. Here, using density functional theory, we investigated the structural, electronic, and electronic transport properties of monolayer (ML), bilayer (BL), and trilayer (TL) PtSe2 on Au(111), PtSe2-X/Au (X = ML, BL, TL). We find the emergence of a chemical interaction at the interface, leading to (i) ohmic contact, (ii) hole doping of PtSe2, and (iii) metallization of the contact layer. In PtSe2-ML/Au, the semiconductor ML becomes metallic, while in PtSe2–BL/Au and PtSe2-TL/Au, the top layers, which do not directly contact Au, become semimetallic. Transport calculations further reveal a thickness-dependent behavior of the electronic transmittance and Schottky barriers along the PtSe2-X channels in contact with the PtSe2-X/Au(111) leads. Based on this atomistic understanding, we propose a heterostructure, Au/PtSe2-TL/Au, where a metal–semiconductor transition can be tuned by mechanical strain. These results highlight the potential of few-layer PtSe2 for two-dimensional electronic devices.
Zanineli, P.; Lopes, E. V. C.; Schleder, G. R.; Lemos, L. N.; Lima, F. Crasto; Fazzio, A.
Heterogeneous Molecular Signatures of Human Odor Perception Miscellaneous
2026.
@misc{zanineli2026heterogeneousmolecularsignatureshuman,
title = {Heterogeneous Molecular Signatures of Human Odor Perception},
author = {P. Zanineli and E. V. C. Lopes and G. R. Schleder and L. N. Lemos and F. Crasto Lima and A. Fazzio},
url = {https://arxiv.org/abs/2604.09758},
year = {2026},
date = {2026-04-10},
urldate = {2026-01-01},
abstract = {Understanding how molecular structure gives rise to odor perception remains a long-standing challenge, with ongoing debate over whether olfaction is primarily governed by molecular shape, vibrational properties, or their interplay at the level of olfactory receptors. Here, we ask whether different odors rely on common molecular determinants or instead emerge from distinct physicochemical regimes. Using interpretable machine-learning models trained on molecular descriptors derived from first-principles calculations that span electronic, vibrational, and structural properties, we analyze feature contributions for odor categories and their associated receptors. We find that no single descriptor class universally dominates odor prediction; instead, different odors exhibit strongly odor-specific patterns of feature importance, with substantial variability across physicochemical domains. This heterogeneity is consistent across different models, suggesting that a universal encoding scheme does not capture odor perception but reflects receptor- and odor-dependent structure-odor relationships. Our results provide statistical constraints on competing olfactory theories and offer a data-driven framework for organizing odor space.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Understanding how molecular structure gives rise to odor perception remains a long-standing challenge, with ongoing debate over whether olfaction is primarily governed by molecular shape, vibrational properties, or their interplay at the level of olfactory receptors. Here, we ask whether different odors rely on common molecular determinants or instead emerge from distinct physicochemical regimes. Using interpretable machine-learning models trained on molecular descriptors derived from first-principles calculations that span electronic, vibrational, and structural properties, we analyze feature contributions for odor categories and their associated receptors. We find that no single descriptor class universally dominates odor prediction; instead, different odors exhibit strongly odor-specific patterns of feature importance, with substantial variability across physicochemical domains. This heterogeneity is consistent across different models, suggesting that a universal encoding scheme does not capture odor perception but reflects receptor- and odor-dependent structure-odor relationships. Our results provide statistical constraints on competing olfactory theories and offer a data-driven framework for organizing odor space.
Zanineli, P.; Lopes, E. V. C.; Schleder, G. R.; Lemos, L. N.; Lima, F. Crasto; Fazzio, A.
Heterogeneous Molecular Signatures of Human Odor Perception Miscellaneous
2026.
@misc{zanineli2026heterogeneousmolecularsignatureshumanb,
title = {Heterogeneous Molecular Signatures of Human Odor Perception},
author = {P. Zanineli and E. V. C. Lopes and G. R. Schleder and L. N. Lemos and F. Crasto Lima and A. Fazzio},
url = {https://arxiv.org/abs/2604.09758},
year = {2026},
date = {2026-04-10},
urldate = {2026-01-01},
abstract = {Understanding how molecular structure gives rise to odor perception remains a long-standing challenge, with ongoing debate over whether olfaction is primarily governed by molecular shape, vibrational properties, or their interplay at the level of olfactory receptors. Here, we ask whether different odors rely on common molecular determinants or instead emerge from distinct physicochemical regimes. Using interpretable machine-learning models trained on molecular descriptors derived from first-principles calculations that span electronic, vibrational, and structural properties, we analyze feature contributions for odor categories and their associated receptors. We find that no single descriptor class universally dominates odor prediction; instead, different odors exhibit strongly odor-specific patterns of feature importance, with substantial variability across physicochemical domains. This heterogeneity is consistent across different models, suggesting that a universal encoding scheme does not capture odor perception but reflects receptor- and odor-dependent structure-odor relationships. Our results provide statistical constraints on competing olfactory theories and offer a data-driven framework for organizing odor space.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Understanding how molecular structure gives rise to odor perception remains a long-standing challenge, with ongoing debate over whether olfaction is primarily governed by molecular shape, vibrational properties, or their interplay at the level of olfactory receptors. Here, we ask whether different odors rely on common molecular determinants or instead emerge from distinct physicochemical regimes. Using interpretable machine-learning models trained on molecular descriptors derived from first-principles calculations that span electronic, vibrational, and structural properties, we analyze feature contributions for odor categories and their associated receptors. We find that no single descriptor class universally dominates odor prediction; instead, different odors exhibit strongly odor-specific patterns of feature importance, with substantial variability across physicochemical domains. This heterogeneity is consistent across different models, suggesting that a universal encoding scheme does not capture odor perception but reflects receptor- and odor-dependent structure-odor relationships. Our results provide statistical constraints on competing olfactory theories and offer a data-driven framework for organizing odor space.
Lopes, Emmanuel V. C.; Lima, Felipe Crasto; Lewenkopf, Caio; Fazzio, Adalberto
Engineering Quantum Phases in Two Dimensions via Vacancy-Induced Electronic Reconstruction Miscellaneous
2026.
@misc{lopes2026engineeringquantumphasesdimensions,
title = {Engineering Quantum Phases in Two Dimensions via Vacancy-Induced Electronic Reconstruction},
author = {Emmanuel V. C. Lopes and Felipe Crasto Lima and Caio Lewenkopf and Adalberto Fazzio},
url = {https://arxiv.org/abs/2603.17122},
year = {2026},
date = {2026-03-17},
urldate = {2026-01-01},
abstract = {Topological phases of matter are commonly understood as emerging either from crystalline symmetry and intrinsic spin-orbit coupling or from disorder-driven electronic renormalization. In realistic materials, however, structural defects naturally combine both ingredients. Here, we demonstrate a general and material-independent mechanism by which atomic vacancies can induce topological phase transitions in two-dimensional semiconductors that are otherwise topologically trivial. Vacancies generate locally ordered dangling-bond states governed by well-defined hopping and spin-orbit interactions, while their spatial distribution and mutual coupling introduce long-range disorder. As vacancy concentration increases, the hybridization of these defect states forms an emergent electronic subspace that undergoes a topological transition. Using a tight-binding framework supported by large-scale density functional theory calculations, we show that this vacancy-induced electronic reconstruction can robustly stabilize quantum spin Hall, quantum anomalous Hall, and Weyl semimetal phases, depending on symmetry breaking and spin polarization. Our results establish vacancies not merely as perturbations, but as active design elements capable of transforming trivial insulators into topological quantum matter, opening realistic routes for defect-engineered topological devices.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Topological phases of matter are commonly understood as emerging either from crystalline symmetry and intrinsic spin-orbit coupling or from disorder-driven electronic renormalization. In realistic materials, however, structural defects naturally combine both ingredients. Here, we demonstrate a general and material-independent mechanism by which atomic vacancies can induce topological phase transitions in two-dimensional semiconductors that are otherwise topologically trivial. Vacancies generate locally ordered dangling-bond states governed by well-defined hopping and spin-orbit interactions, while their spatial distribution and mutual coupling introduce long-range disorder. As vacancy concentration increases, the hybridization of these defect states forms an emergent electronic subspace that undergoes a topological transition. Using a tight-binding framework supported by large-scale density functional theory calculations, we show that this vacancy-induced electronic reconstruction can robustly stabilize quantum spin Hall, quantum anomalous Hall, and Weyl semimetal phases, depending on symmetry breaking and spin polarization. Our results establish vacancies not merely as perturbations, but as active design elements capable of transforming trivial insulators into topological quantum matter, opening realistic routes for defect-engineered topological devices.
2025
Araújo, Augusto L.; Sophia, Pedro H.; Lima, F. Crasto; Fazzio, Adalberto
A high-throughput framework and database for twisted 2D van der Waals bilayers Journal Article
Em: npj Comput Mater, 2025, ISSN: 2057-3960.
@article{Araújo2025,
title = {A high-throughput framework and database for twisted 2D van der Waals bilayers},
author = {Augusto L. Araújo and Pedro H. Sophia and F. Crasto Lima and Adalberto Fazzio},
doi = {10.1038/s41524-025-01892-z},
issn = {2057-3960},
year = {2025},
date = {2025-12-20},
urldate = {2025-12-20},
journal = {npj Comput Mater},
publisher = {Springer Science and Business Media LLC},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>Twisted two-dimensional van der Waals heterostructures provide a fertile ground for tailoring electronic and structural properties. However, their vast configurational space poses challenges for systematic study. Here, we introduce SAMBA, an open-source, high-throughput Python workflow that automates the generation, simulation, and analysis of twisted bilayers. Using the coincidence lattice method, we generate a comprehensive set of over 18,000 quasi-commensurable homo- and heterobilayer structures based on 63 experimentally reported monolayers, and perform DFT simulations on a growing subset. The resulting database includes symmetry, interlayer energetics, band alignment, and charge transfer. A detailed case study on graphene-jacutingaite illustrates the framework’s capabilities. This platform offers a robust foundation for data-driven discovery and the rational design of 2D materials with tunable properties.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>Twisted two-dimensional van der Waals heterostructures provide a fertile ground for tailoring electronic and structural properties. However, their vast configurational space poses challenges for systematic study. Here, we introduce SAMBA, an open-source, high-throughput Python workflow that automates the generation, simulation, and analysis of twisted bilayers. Using the coincidence lattice method, we generate a comprehensive set of over 18,000 quasi-commensurable homo- and heterobilayer structures based on 63 experimentally reported monolayers, and perform DFT simulations on a growing subset. The resulting database includes symmetry, interlayer energetics, band alignment, and charge transfer. A detailed case study on graphene-jacutingaite illustrates the framework’s capabilities. This platform offers a robust foundation for data-driven discovery and the rational design of 2D materials with tunable properties.</jats:p>
<jats:p>Twisted two-dimensional van der Waals heterostructures provide a fertile ground for tailoring electronic and structural properties. However, their vast configurational space poses challenges for systematic study. Here, we introduce SAMBA, an open-source, high-throughput Python workflow that automates the generation, simulation, and analysis of twisted bilayers. Using the coincidence lattice method, we generate a comprehensive set of over 18,000 quasi-commensurable homo- and heterobilayer structures based on 63 experimentally reported monolayers, and perform DFT simulations on a growing subset. The resulting database includes symmetry, interlayer energetics, band alignment, and charge transfer. A detailed case study on graphene-jacutingaite illustrates the framework’s capabilities. This platform offers a robust foundation for data-driven discovery and the rational design of 2D materials with tunable properties.</jats:p>
Neves, Matheus F. F.; Barêa, Heloísa M.; Perfecto, Tarcísio; Bettini, Jefferson; Lima, Felipe Crasto; Oliveira, Rafael F.; Fazzio, Adalberto; Leite, Edson R.; Santhiago, Murilo
Room‐Temperature Tuning of Electrical Conductivity in Single MoS_2 Flakes via Nanoscale Amorphization by Focused Ion Beam Journal Article
Em: Adv Materials Technologies, 2025, ISSN: 2365-709X.
@article{dasNeves2025,
title = {Room‐Temperature Tuning of Electrical Conductivity in Single MoS_2 Flakes via Nanoscale Amorphization by Focused Ion Beam},
author = {Matheus F. F. Neves and Heloísa M. Barêa and Tarcísio Perfecto and Jefferson Bettini and Felipe Crasto Lima and Rafael F. Oliveira and Adalberto Fazzio and Edson R. Leite and Murilo Santhiago},
doi = {10.1002/admt.202501505},
issn = {2365-709X},
year = {2025},
date = {2025-09-09},
urldate = {2025-09-09},
journal = {Adv Materials Technologies},
publisher = {Wiley},
abstract = {<jats:title>Abstract</jats:title><jats:p>High spatially resolved defect engineering via local amorphization enables controlled processing of materials with enhanced electrical properties and catalytic sites, offering prospects for electronics and hydrogen evolution applications. The intriguing electrical properties of amorphous Molybdenum Disulfide (MoS<jats:sub>2</jats:sub>) open opportunities for electrical and electrochemical devices. However, controlling electrical features in miniaturized devices with minimal carbon contamination under mild conditions remains challenging. Here, the obtention of ultra‐large MoS<jats:sub>2</jats:sub> monolayers is reported, and fine‐tune defect insertion in a single flake using focused ion beam at room temperature. By controlling defect density on electrochemically thinned samples, electrical conductivity increases by one order of magnitude. The width of the conductive amorphous channels can be tuned in a dose‐dependent fashion down to ≈700 nm. Defect types, including amorphized areas, are identified by high‐resolution transmission electron microscopy. Finally, insights into the origin of the higher conductivity in amorphous MoS<jats:sub>2</jats:sub> are obtained using density functional theory and ab initio molecular dynamics simulations on structures with varying stoichiometry and vacancy types. These findings enable precise tuning of electrical properties under mild conditions using high‐aspect ratio pristine MoS<jats:sub>2</jats:sub> layers.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title><jats:p>High spatially resolved defect engineering via local amorphization enables controlled processing of materials with enhanced electrical properties and catalytic sites, offering prospects for electronics and hydrogen evolution applications. The intriguing electrical properties of amorphous Molybdenum Disulfide (MoS<jats:sub>2</jats:sub>) open opportunities for electrical and electrochemical devices. However, controlling electrical features in miniaturized devices with minimal carbon contamination under mild conditions remains challenging. Here, the obtention of ultra‐large MoS<jats:sub>2</jats:sub> monolayers is reported, and fine‐tune defect insertion in a single flake using focused ion beam at room temperature. By controlling defect density on electrochemically thinned samples, electrical conductivity increases by one order of magnitude. The width of the conductive amorphous channels can be tuned in a dose‐dependent fashion down to ≈700 nm. Defect types, including amorphized areas, are identified by high‐resolution transmission electron microscopy. Finally, insights into the origin of the higher conductivity in amorphous MoS<jats:sub>2</jats:sub> are obtained using density functional theory and ab initio molecular dynamics simulations on structures with varying stoichiometry and vacancy types. These findings enable precise tuning of electrical properties under mild conditions using high‐aspect ratio pristine MoS<jats:sub>2</jats:sub> layers.</jats:p>
Sandoval, M. A. Toloza; Freire, R. L. H.; Araújo, A. L.; Acosta, Carlos Mera; Lima, F. Crasto; Fazzio, A.
Orbital filtering in edge-state transport of PbSe nanoribbons Journal Article
Em: Phys. Rev. Materials, vol. 9, não 9, 2025, ISSN: 2475-9953.
@article{Sandoval2025,
title = {Orbital filtering in edge-state transport of PbSe nanoribbons},
author = {M. A. Toloza Sandoval and R. L. H. Freire and A. L. Araújo and Carlos Mera Acosta and F. Crasto Lima and A. Fazzio},
doi = {10.1103/ttfc-9z7d},
issn = {2475-9953},
year = {2025},
date = {2025-09-02},
journal = {Phys. Rev. Materials},
volume = {9},
number = {9},
publisher = {American Physical Society (APS)},
abstract = {Topological insulators are expected to exhibit robust edge-state transport protected by time-reversal symmetry, yet experimental conductance often falls below the quantized limit due to intrinsic and interfacial effects. Here, we demonstrate that the orbital character of topological edge states, governed by spin-orbit coupling and edge termination, plays a critical role in electron injection and transport. Using first-principles calculations combined with nonequilibrium Green's function methods, we investigate PbSe nanoribbons as a model system. We identify an orbital filtering mechanism arising from spin-orbital-entangled edge states, where the 𝑗=1/2 and 𝑗=3/2 components of the 𝑝 orbitals obey symmetry-imposed selection rules at the interface. This effect limits conductance even in the absence of disorder; when present, disorder further promotes an interplay between topological edge states and resonant edge-localized states originating from dangling bonds. Our findings highlight the importance of orbital engineering and angular momentum symmetry mismatch in the design of topological devices and call for an examination of interface physics in quantum materials regarding the topological protection.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Topological insulators are expected to exhibit robust edge-state transport protected by time-reversal symmetry, yet experimental conductance often falls below the quantized limit due to intrinsic and interfacial effects. Here, we demonstrate that the orbital character of topological edge states, governed by spin-orbit coupling and edge termination, plays a critical role in electron injection and transport. Using first-principles calculations combined with nonequilibrium Green's function methods, we investigate PbSe nanoribbons as a model system. We identify an orbital filtering mechanism arising from spin-orbital-entangled edge states, where the 𝑗=1/2 and 𝑗=3/2 components of the 𝑝 orbitals obey symmetry-imposed selection rules at the interface. This effect limits conductance even in the absence of disorder; when present, disorder further promotes an interplay between topological edge states and resonant edge-localized states originating from dangling bonds. Our findings highlight the importance of orbital engineering and angular momentum symmetry mismatch in the design of topological devices and call for an examination of interface physics in quantum materials regarding the topological protection.
Sandoval, M. A. Toloza; Freire, R. L. H.; Araújo, A. L.; Acosta, Carlos Mera; Lima, F. Crasto; Fazzio, A.
Orbital filtering in edge-state transport of PbSe nanoribbons Journal Article
Em: Phys. Rev. Materials, vol. 9, não 9, 2025, ISSN: 2475-9953.
@article{Sandoval2025b,
title = {Orbital filtering in edge-state transport of PbSe nanoribbons},
author = {M. A. Toloza Sandoval and R. L. H. Freire and A. L. Araújo and Carlos Mera Acosta and F. Crasto Lima and A. Fazzio},
doi = {10.1103/ttfc-9z7d},
issn = {2475-9953},
year = {2025},
date = {2025-09-01},
journal = {Phys. Rev. Materials},
volume = {9},
number = {9},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
DesRoche, Emmett; Lima, Felipe Crasto; Groome, Ryan R. K.; Furlan, Michael; Tumino, Francesco; Inayeh, Alex; Aloisio, Mark D.; Singh, Ishwar; Veinot, Alex J.; Miwa, Roberto H.; Crudden, Cathleen M.; McLean, Alastair B.
Mechanisms of N-Heterocyclic Carbene Complex Lattice Formation Journal Article
Em: ACS Nano, 2025, ISSN: 1936-086X.
@article{DesRoche2025,
title = {Mechanisms of N-Heterocyclic Carbene Complex Lattice Formation},
author = {Emmett DesRoche and Felipe Crasto Lima and Ryan R. K. Groome and Michael Furlan and Francesco Tumino and Alex Inayeh and Mark D. Aloisio and Ishwar Singh and Alex J. Veinot and Roberto H. Miwa and Cathleen M. Crudden and Alastair B. McLean},
doi = {10.1021/acsnano.5c06139},
issn = {1936-086X},
year = {2025},
date = {2025-08-25},
urldate = {2025-08-25},
journal = {ACS Nano},
publisher = {American Chemical Society (ACS)},
abstract = {N-Heterocyclic carbenes (NHCs) that have wingtip groups with low steric bulk, such as 1,3-dimethyl-benzimidazol-2-ylidene (NHCMe), form bis-complexes with metal atoms when they are deposited onto Au(111) surfaces in vacuo. These complexes self-assemble into three different lattices: a herringbone, a double-herringbone, and a chiral kagome lattice. The static properties of these lattices have been studied with scanning tunneling microscopy and ab initio theoretical methods. Dynamic processes including complex center displacement and hindered monomer motion have also been observed. Our results suggest that in addition to surface hopping, exchange processes are important, providing a facile mechanism for atom exchange between the overlayer and the metal. These dynamic processes are well-known from studies of metal epitaxy but have not previously been discussed in the context of NHC self-assembly.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
N-Heterocyclic carbenes (NHCs) that have wingtip groups with low steric bulk, such as 1,3-dimethyl-benzimidazol-2-ylidene (NHCMe), form bis-complexes with metal atoms when they are deposited onto Au(111) surfaces in vacuo. These complexes self-assemble into three different lattices: a herringbone, a double-herringbone, and a chiral kagome lattice. The static properties of these lattices have been studied with scanning tunneling microscopy and ab initio theoretical methods. Dynamic processes including complex center displacement and hindered monomer motion have also been observed. Our results suggest that in addition to surface hopping, exchange processes are important, providing a facile mechanism for atom exchange between the overlayer and the metal. These dynamic processes are well-known from studies of metal epitaxy but have not previously been discussed in the context of NHC self-assembly.
Vidarte, Kevin J. U.; Lewenkopf, Caio; Lima, F. Crasto; Miwa, R. Hiroki; Riffo, Felipe Pérez; Morell, Eric Suárez
Unveiling the Electronic Origin of Anomalous Contact Conductance in Twisted Bilayer Graphene Miscellaneous
2025.
@misc{vidarte2025unveilingelectronicoriginanomalous,
title = {Unveiling the Electronic Origin of Anomalous Contact Conductance in Twisted Bilayer Graphene},
author = {Kevin J. U. Vidarte and Caio Lewenkopf and F. Crasto Lima and R. Hiroki Miwa and Felipe Pérez Riffo and Eric Suárez Morell},
url = {https://arxiv.org/abs/2506.21721},
year = {2025},
date = {2025-06-26},
urldate = {2025-01-01},
abstract = {This study theoretically investigates the contact conductance in twisted bilayer graphene (TBG), providing a theoretical explanation for recent experimental observations from scanning tunneling microscopy (STM) and conductive atomic force microscopy (c-AFM). These experiments revealed a surprising non-monotonic current pattern as a function of the TBG rotation angle θ, with a peak at θ ≈ 5 ◦, a finding that markedly departs from the well-known magic angle TBG behavior. To elucidate this phenomenon, we develop a comprehensive theoretical and computational framework. Our calculations, performed on both relaxed and rigid TBG structures, simulate contact conductance by analyzing the local density of states across a range of biases and rotational angles. Contrary to the current interpretation, our results demonstrate that the maximum conductance at θ ≈ 5 o is not caused by structural relaxation or AA stacking zone changes. Instead, we attribute this peak
to the evolution of the electronic band structure, specifically the shifting of van Hove singularities (vHs) to the Fermi level as the twist angle decreases. We further show that the precise location of this conductance maximum is dependent on the applied bias voltage. This interplay between twist angle, bias, and vHs energy provides a robust explanation for the experimental findings.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
This study theoretically investigates the contact conductance in twisted bilayer graphene (TBG), providing a theoretical explanation for recent experimental observations from scanning tunneling microscopy (STM) and conductive atomic force microscopy (c-AFM). These experiments revealed a surprising non-monotonic current pattern as a function of the TBG rotation angle θ, with a peak at θ ≈ 5 ◦, a finding that markedly departs from the well-known magic angle TBG behavior. To elucidate this phenomenon, we develop a comprehensive theoretical and computational framework. Our calculations, performed on both relaxed and rigid TBG structures, simulate contact conductance by analyzing the local density of states across a range of biases and rotational angles. Contrary to the current interpretation, our results demonstrate that the maximum conductance at θ ≈ 5 o is not caused by structural relaxation or AA stacking zone changes. Instead, we attribute this peak
to the evolution of the electronic band structure, specifically the shifting of van Hove singularities (vHs) to the Fermi level as the twist angle decreases. We further show that the precise location of this conductance maximum is dependent on the applied bias voltage. This interplay between twist angle, bias, and vHs energy provides a robust explanation for the experimental findings.
to the evolution of the electronic band structure, specifically the shifting of van Hove singularities (vHs) to the Fermi level as the twist angle decreases. We further show that the precise location of this conductance maximum is dependent on the applied bias voltage. This interplay between twist angle, bias, and vHs energy provides a robust explanation for the experimental findings.
Lima, F. Crasto; Miwa, Roberto H.; Lewenkopf, Caio; Fazzio, Adalberto
Interacting virtual topological phases in defect-rich two-dimensional materials Journal Article
Em: Phys. Rev. B, vol. 111, não 19, 2025, ISSN: 2469-9969.
@article{deLima2025,
title = {Interacting virtual topological phases in defect-rich two-dimensional materials},
author = {F. Crasto Lima and Roberto H. Miwa and Caio Lewenkopf and Adalberto Fazzio},
doi = {10.1103/physrevb.111.195135},
issn = {2469-9969},
year = {2025},
date = {2025-05-19},
journal = {Phys. Rev. B},
volume = {111},
number = {19},
publisher = {American Physical Society (APS)},
abstract = {We investigate the robustness of virtual topological states—topological phases away from the Fermi energy—against the electron-electron interaction and band filling. As a case study, we employ a realistic model to investigate the properties of vacancy-driven topological phases in transition metal dichalcogenides (TMDs) and establish a connection between the degree of localization of topological wave functions, the vacancy density, and the electron-electron interaction strength with the topological phase robustness. We demonstrate that electron-electron interactions play a crucial role in degrading topological phases thereby determining the validity of single-particle approximations for topological insulator phases. Our findings can be naturally extended to virtual topological phases of a wide range of materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We investigate the robustness of virtual topological states—topological phases away from the Fermi energy—against the electron-electron interaction and band filling. As a case study, we employ a realistic model to investigate the properties of vacancy-driven topological phases in transition metal dichalcogenides (TMDs) and establish a connection between the degree of localization of topological wave functions, the vacancy density, and the electron-electron interaction strength with the topological phase robustness. We demonstrate that electron-electron interactions play a crucial role in degrading topological phases thereby determining the validity of single-particle approximations for topological insulator phases. Our findings can be naturally extended to virtual topological phases of a wide range of materials.
Lima, F. Crasto; Miwa, Roberto H.; Lewenkopf, Caio; Fazzio, Adalberto
Interacting virtual topological phases in defect-rich two-dimensional materials Journal Article
Em: Phys. Rev. B, vol. 111, não 19, 2025, ISSN: 2469-9969.
@article{deLima2025b,
title = {Interacting virtual topological phases in defect-rich two-dimensional materials},
author = {F. Crasto Lima and Roberto H. Miwa and Caio Lewenkopf and Adalberto Fazzio},
doi = {10.1103/physrevb.111.195135},
issn = {2469-9969},
year = {2025},
date = {2025-05-01},
journal = {Phys. Rev. B},
volume = {111},
number = {19},
publisher = {American Physical Society (APS)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2024
Lima, F. Crasto; Miwa, Roberto H.; Lewenkopf, Caio; Fazzio, Adalberto
Interacting Virtual Topological Phases in Defect-Rich 2D Materials Working paper
2024.
@workingpaper{delima2024interactingvirtualtopologicalphases,
title = {Interacting Virtual Topological Phases in Defect-Rich 2D Materials},
author = {F. Crasto Lima and Roberto H. Miwa and Caio Lewenkopf and Adalberto Fazzio},
url = {https://arxiv.org/abs/2412.08607},
year = {2024},
date = {2024-12-11},
urldate = {2024-01-01},
abstract = {We investigate the robustness of it virtual topological states – topological phases away from the Fermi energy – against the electron-electron interaction and band filling. As a case study, we employ a realistic model to investigate the properties of vacancy-driven topological phases in transition metal dichalcogenides (TMDs) and establish a connection between the degree of localization of topological wave functions, the vacancy density, and the electron-electron interaction strength with the topological phase robustness. We demonstrate that electron-electron interactions play a crucial role in degrading topological phases thereby determining the validity of single-particle approximations for topological insulator phases. Our findings can be naturally extended to virtual topological phases of a wide range of materials.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
We investigate the robustness of it virtual topological states – topological phases away from the Fermi energy – against the electron-electron interaction and band filling. As a case study, we employ a realistic model to investigate the properties of vacancy-driven topological phases in transition metal dichalcogenides (TMDs) and establish a connection between the degree of localization of topological wave functions, the vacancy density, and the electron-electron interaction strength with the topological phase robustness. We demonstrate that electron-electron interactions play a crucial role in degrading topological phases thereby determining the validity of single-particle approximations for topological insulator phases. Our findings can be naturally extended to virtual topological phases of a wide range of materials.
Petry, Romana; Almeida, James M.; Côa, Francine; Lima, F. Crasto; Martinez, Diego Stéfani T; Fazzio, Adalberto
Interaction of graphene oxide with tannic acid: computational modeling and toxicity mitigation in C. elegans Journal Article
Em: Beilstein J. Nanotechnol., vol. 15, pp. 1297–1311, 2024, ISSN: 2190-4286.
@article{Petry2024,
title = {Interaction of graphene oxide with tannic acid: computational modeling and toxicity mitigation in C. elegans},
author = {Romana Petry and James M. Almeida and Francine Côa and F. Crasto Lima and Diego Stéfani T Martinez and Adalberto Fazzio},
doi = {10.3762/bjnano.15.105},
issn = {2190-4286},
year = {2024},
date = {2024-10-30},
urldate = {2024-10-30},
journal = {Beilstein J. Nanotechnol.},
volume = {15},
pages = {1297–1311},
publisher = {Beilstein Institut},
abstract = {Graphene oxide (GO) undergoes multiple transformations when introduced to biological and environmental media. GO surface favors the adsorption of biomolecules through different types of interaction mechanisms, modulating the biological effects of the material. In this study, we investigated the interaction of GO with tannic acid (TA) and its consequences for GO toxicity. We focused on understanding how TA interacts with GO, its impact on the material surface chemistry, colloidal stability, as well as, toxicity and biodistribution using the Caenorhabditis elegans model. Employing computational modeling, including reactive classical molecular dynamics and ab initio calculations, we reveal that TA preferentially binds to the most reactive sites on GO surfaces via the oxygen-containing groups or the carbon matrix; van der Waals interaction forces dominate the binding energy. TA exhibits a dose-dependent mitigating effect on the toxicity of GO, which can be attributed not only to the surface interactions between the molecule and the material but also to the inherent biological properties of TA in C. elegans. Our findings contribute to a deeper understanding of GO’s environmental behavior and toxicity and highlight the potential of tannic acid for the synthesis and surface functionalization of graphene-based nanomaterials, offering insights into safer nanotechnology development.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphene oxide (GO) undergoes multiple transformations when introduced to biological and environmental media. GO surface favors the adsorption of biomolecules through different types of interaction mechanisms, modulating the biological effects of the material. In this study, we investigated the interaction of GO with tannic acid (TA) and its consequences for GO toxicity. We focused on understanding how TA interacts with GO, its impact on the material surface chemistry, colloidal stability, as well as, toxicity and biodistribution using the Caenorhabditis elegans model. Employing computational modeling, including reactive classical molecular dynamics and ab initio calculations, we reveal that TA preferentially binds to the most reactive sites on GO surfaces via the oxygen-containing groups or the carbon matrix; van der Waals interaction forces dominate the binding energy. TA exhibits a dose-dependent mitigating effect on the toxicity of GO, which can be attributed not only to the surface interactions between the molecule and the material but also to the inherent biological properties of TA in C. elegans. Our findings contribute to a deeper understanding of GO’s environmental behavior and toxicity and highlight the potential of tannic acid for the synthesis and surface functionalization of graphene-based nanomaterials, offering insights into safer nanotechnology development.
Lemos, Victor Secco; Moraes, Daniel Angeli; Pataca, Iara Lacerda; Verruma, Olavo Fiamencini; Torres, Carolina Pirogini; Albuquerque, Angela; Rodríguez-Gutiérrez, Ingrid; Janes, Danilo Biazon; Lima, F. Crasto; Souza, Flavio Leandro; Leite, Edson Roberto; Fazzio, Adalberto; Junior, João Batista Souza
Platinum Selenide Nanoparticle Synthesis and Reaction with Butyllithium Breaking the Long-Range Ordering Structure Journal Article
Em: Chem. Mater., 2024, ISSN: 1520-5002.
@article{Lemos2024,
title = {Platinum Selenide Nanoparticle Synthesis and Reaction with Butyllithium Breaking the Long-Range Ordering Structure},
author = {Victor Secco Lemos and Daniel Angeli Moraes and Iara Lacerda Pataca and Olavo Fiamencini Verruma and Carolina Pirogini Torres and Angela Albuquerque and Ingrid Rodríguez-Gutiérrez and Danilo Biazon Janes and F. Crasto Lima and Flavio Leandro Souza and Edson Roberto Leite and Adalberto Fazzio and João Batista Souza Junior},
url = {https://pubs.acs.org/doi/abs/10.1021/acs.chemmater.4c00753},
doi = {10.1021/acs.chemmater.4c00753},
issn = {1520-5002},
year = {2024},
date = {2024-09-10},
urldate = {2024-09-10},
journal = {Chem. Mater.},
publisher = {American Chemical Society (ACS)},
abstract = {PtSe2 is a transition metal dichalcogenide (TMD) material with a broad range of applications, such as sensors, electronics, and catalysis. Although 2D monolayers of PtSe2 have been widely studied, the synthesis of controlled PtSe2 nanoparticles (NPs) is still unexplored. Here, the new strategy to synthesize PtSe2 NPs was to react Pt NPs with selenium in a liquid state inside a homemade closed reactor. Afterward, the PtSe2 NPs reaction with butyllithium led to cleavage of the covalent bond along the ab-plane of 2D material (intralayer) and broke the PtSe2 long-range structure. The result was a PtSex nanomaterial with a greater concentration of defects having only the short-range ordering but keeping the local structure, as proved by Raman and ePDF analyses. X-ray photoelectron spectroscopy revealed a higher contribution from defects (Pt 4f ∼72 eV) for PtSex compared to the crystalline PtSe2 chemical environment (∼73.2 eV), probably due to the creation of edges on the surface of PtSex. PtSe2, and PtSex NPs’ performance toward the hydrogen evolution reaction (HER) application was tested, which indicated a better efficiency than bulk PtSe2. However, the disordered PtSex sample has better electrocatalytic activity, as the number of defects and increased edge exposure create more active sites. Therefore, the results reported here indicate that PtSe2 NPs can be produced using a fast and simple method compared to standard selenization processes, and the activation toward the HER was further enhanced by defect engineering.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
PtSe2 is a transition metal dichalcogenide (TMD) material with a broad range of applications, such as sensors, electronics, and catalysis. Although 2D monolayers of PtSe2 have been widely studied, the synthesis of controlled PtSe2 nanoparticles (NPs) is still unexplored. Here, the new strategy to synthesize PtSe2 NPs was to react Pt NPs with selenium in a liquid state inside a homemade closed reactor. Afterward, the PtSe2 NPs reaction with butyllithium led to cleavage of the covalent bond along the ab-plane of 2D material (intralayer) and broke the PtSe2 long-range structure. The result was a PtSex nanomaterial with a greater concentration of defects having only the short-range ordering but keeping the local structure, as proved by Raman and ePDF analyses. X-ray photoelectron spectroscopy revealed a higher contribution from defects (Pt 4f ∼72 eV) for PtSex compared to the crystalline PtSe2 chemical environment (∼73.2 eV), probably due to the creation of edges on the surface of PtSex. PtSe2, and PtSex NPs’ performance toward the hydrogen evolution reaction (HER) application was tested, which indicated a better efficiency than bulk PtSe2. However, the disordered PtSex sample has better electrocatalytic activity, as the number of defects and increased edge exposure create more active sites. Therefore, the results reported here indicate that PtSe2 NPs can be produced using a fast and simple method compared to standard selenization processes, and the activation toward the HER was further enhanced by defect engineering.
Araújo, Augusto L.; Lima, F. Crasto; Fazzio, Adalberto
Reentrant topological phase in half-Heusler compounds Miscellaneous
2024.
@misc{araújo2024reentranttopologicalphasehalfheusler,
title = {Reentrant topological phase in half-Heusler compounds},
author = {Augusto L. Araújo and F. Crasto Lima and Adalberto Fazzio},
url = {https://arxiv.org/abs/2409.01385},
year = {2024},
date = {2024-09-02},
urldate = {2024-01-01},
abstract = {Half-Heusler compounds are known for their various compositions and multifunctional properties including topological phases. In this study, we investigate the topological classification of this class of materials based on the ordering of the Γ6, Γ8 states, and a previously overlooked Γ∗6 state, during an adiabatic expansion process. Using first-principles calculations based on density functional theory, we observed that the non-trivial topology is governed by a three-band mechanism. We provide a simple model derived from k⋅p Hamiltonian that interprets the topological phase in half-Heusler systems. Additionally, we explore the robustness of the topological phase under tension and a new perspective on the topological nature of half-Heusler compounds.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Half-Heusler compounds are known for their various compositions and multifunctional properties including topological phases. In this study, we investigate the topological classification of this class of materials based on the ordering of the Γ6, Γ8 states, and a previously overlooked Γ∗6 state, during an adiabatic expansion process. Using first-principles calculations based on density functional theory, we observed that the non-trivial topology is governed by a three-band mechanism. We provide a simple model derived from k⋅p Hamiltonian that interprets the topological phase in half-Heusler systems. Additionally, we explore the robustness of the topological phase under tension and a new perspective on the topological nature of half-Heusler compounds.
Freire, Rafael L. H.; Lima, F. Crasto; Miwa, Roberto H.; Fazzio, Adalberto
Exploring topological transport in Pt2HgSe3 nanoribbons: Insights for spintronic device integration Journal Article
Em: Phys. Rev. B, vol. 110, iss. 3, pp. 035111, 2024.
@article{PhysRevB.110.035111,
title = {Exploring topological transport in Pt2HgSe3 nanoribbons: Insights for spintronic device integration},
author = {Rafael L. H. Freire and F. Crasto Lima and Roberto H. Miwa and Adalberto Fazzio},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.035111},
doi = {10.1103/PhysRevB.110.035111},
year = {2024},
date = {2024-07-02},
urldate = {2024-07-01},
journal = {Phys. Rev. B},
volume = {110},
issue = {3},
pages = {035111},
publisher = {American Physical Society},
abstract = {The discovery of the quantum spin Hall effect led to the exploration of the electronic transport for spintronic devices. We theoretically investigated the electronic conductance in large-gap realistic quantum spin Hall system Pt2HgSe3 nanoribbons. By an ab initio approach, we found that the edge states present a penetration depth of about 0.9 nm, much smaller than those predicted in other two-dimensional topological systems, thus, suggesting that Pt2HgSe3 allows the exploitation of topological transport properties in narrow ribbons. Using nonequilibrium Green's function calculations, we have examined the electron conductivity upon the presence of Se↔Hg antistructure defects randomly distributed in the Pt2HgSe3 scattering region. By considering scattering lengths up to 109 nm, we found localization lengths that can surpass micrometer sizes for narrow nanoribbons (<9 nm). These findings can contribute to further understanding the behavior of topological insulators under realistic conditions and their integration within electronic spintronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The discovery of the quantum spin Hall effect led to the exploration of the electronic transport for spintronic devices. We theoretically investigated the electronic conductance in large-gap realistic quantum spin Hall system Pt2HgSe3 nanoribbons. By an ab initio approach, we found that the edge states present a penetration depth of about 0.9 nm, much smaller than those predicted in other two-dimensional topological systems, thus, suggesting that Pt2HgSe3 allows the exploitation of topological transport properties in narrow ribbons. Using nonequilibrium Green's function calculations, we have examined the electron conductivity upon the presence of Se↔Hg antistructure defects randomly distributed in the Pt2HgSe3 scattering region. By considering scattering lengths up to 109 nm, we found localization lengths that can surpass micrometer sizes for narrow nanoribbons (<9 nm). These findings can contribute to further understanding the behavior of topological insulators under realistic conditions and their integration within electronic spintronic devices.
Cunha, Rafael O.; Garcia-Basabe, Yunier; Larrude, Dunieskys G.; Gamino, Matheus; Lima, Erika Nascimento; Lima, F. Crasto; Fazzio, Adalberto; Rezende, Sergio M.; Azevedo, Antonio; Mendes, Joaquim B. S.
2024.
@workingpaper{cunha2024unraveling,
title = {Unraveling the Spin-to-Charge Current Conversion Mechanism and Charge Transfer Dynamics at Interface of Graphene/WS$_2$ Heterostructures at Room Temperature},
author = {Rafael O. Cunha and Yunier Garcia-Basabe and Dunieskys G. Larrude and Matheus Gamino and Erika Nascimento Lima and F. Crasto Lima and Adalberto Fazzio and Sergio M. Rezende and Antonio Azevedo and Joaquim B. S. Mendes},
url = {https://arxiv.org/abs/2405.18617},
year = {2024},
date = {2024-05-28},
urldate = {2024-01-01},
abstract = {We report experimental investigations of spin-to-charge current conversion and charge transfer dynamics (CT) at the interface of graphene/WS2 van der Waals heterostructure. Pure spin current was produced by the spin precession in the microwave-driven ferromagnetic resonance of a permalloy film (Py-Ni81Fe19) and injected into the graphene/WS2 heterostructure through the spin pumping process. The observed spin-to-charge current conversion in the heterostructure is attributed to inverse Rashba-Edelstein effect (IREE) at the graphene/WS2 interface. Interfacial CT dynamics in this heterostructure was investigated based on the framework of core-hole-clock (CHC) approach. The results obtained from spin pumping and CHC studies show that the spin-to-charge current conversion and charge transfer process are more efficient in the graphene/WS2 heterostructure compared to isolated WS2 and graphene films. The results show that the presence of WS2 flakes improves the current conversion efficiency. These experimental results are corroborated by density functional theory (DFT) calculations, which reveal (i) Rashba spin-orbit splitting of graphene orbitals and (ii) electronic coupling between graphene and WS2 orbitals. This study provides valuable insights for optimizing the design and performance of s},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
We report experimental investigations of spin-to-charge current conversion and charge transfer dynamics (CT) at the interface of graphene/WS2 van der Waals heterostructure. Pure spin current was produced by the spin precession in the microwave-driven ferromagnetic resonance of a permalloy film (Py-Ni81Fe19) and injected into the graphene/WS2 heterostructure through the spin pumping process. The observed spin-to-charge current conversion in the heterostructure is attributed to inverse Rashba-Edelstein effect (IREE) at the graphene/WS2 interface. Interfacial CT dynamics in this heterostructure was investigated based on the framework of core-hole-clock (CHC) approach. The results obtained from spin pumping and CHC studies show that the spin-to-charge current conversion and charge transfer process are more efficient in the graphene/WS2 heterostructure compared to isolated WS2 and graphene films. The results show that the presence of WS2 flakes improves the current conversion efficiency. These experimental results are corroborated by density functional theory (DFT) calculations, which reveal (i) Rashba spin-orbit splitting of graphene orbitals and (ii) electronic coupling between graphene and WS2 orbitals. This study provides valuable insights for optimizing the design and performance of s
Sandoval, M. A. Toloza; Araújo, A. L.; Lima, F. Crasto; Fazzio, Adalberto
Resonant helical multi-edge transport in Sierpiński carpets Working paper
2024.
@workingpaper{sandoval2024resonant,
title = {Resonant helical multi-edge transport in Sierpiński carpets},
author = {M. A. Toloza Sandoval and A. L. Araújo and F. Crasto Lima and Adalberto Fazzio},
url = {https://arxiv.org/abs/2401.16014},
doi = {https://doi.org/10.48550/arXiv.2401.16014},
year = {2024},
date = {2024-01-29},
urldate = {2024-01-29},
abstract = {In recent years, synthesis and experimental research of fractalized materials has evolved in a paradigmatic crossover with topological phases of matter. We present here a theoretical investigation of the helical edge transport in Sierpinski carpets (SCs), combining the Bernevig-Hughes-Zhang (BHZ) model and the Landauer approach. Starting from a pristine two-dimensional topological insulator (2DTI), according to the BHZ model, our results reveal resonant transport modes when the SC fractal generation reaches the same scale as the space discretization; these modes are analyzed within a contour plot mapping of the local spin-polarized currents, shown spanned and assisted by inner-edge channels. From such a deeply fractalized SC building block, we introduce a rich tapestry formed by superior SC hierarchies, enlightening intricate patterns and unique fingerprints that offer valuable insights into how helical edge transport occurs in these fractal dimensions.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
In recent years, synthesis and experimental research of fractalized materials has evolved in a paradigmatic crossover with topological phases of matter. We present here a theoretical investigation of the helical edge transport in Sierpinski carpets (SCs), combining the Bernevig-Hughes-Zhang (BHZ) model and the Landauer approach. Starting from a pristine two-dimensional topological insulator (2DTI), according to the BHZ model, our results reveal resonant transport modes when the SC fractal generation reaches the same scale as the space discretization; these modes are analyzed within a contour plot mapping of the local spin-polarized currents, shown spanned and assisted by inner-edge channels. From such a deeply fractalized SC building block, we introduce a rich tapestry formed by superior SC hierarchies, enlightening intricate patterns and unique fingerprints that offer valuable insights into how helical edge transport occurs in these fractal dimensions.
Freire, Rafael L. H.; Lima, F. Crasto; Miwa, Roberto H.; Fazzio, Adalberto
Exploring Topological Transport in Pt$_2$HgSe$_3$ Nanoribbons: Insights for Spintronic Device Integration Working paper
2024.
@workingpaper{freire2024exploring,
title = {Exploring Topological Transport in Pt$_2$HgSe$_3$ Nanoribbons: Insights for Spintronic Device Integration},
author = {Rafael L. H. Freire and F. Crasto Lima and Roberto H. Miwa and Adalberto Fazzio},
url = {https://arxiv.org/abs/2405.06861v1},
doi = {https://doi.org/10.48550/arXiv.2405.06861},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
abstract = {The discovery of the quantum spin Hall effect led to the exploration of the electronic transport for spintronic devices. Here, we theoretically investigated the electronic conductance in large-gap realistic quantum spin Hall system, Pt2HgSe3 nanoribbons. By an ab initio approach, we found that the edge states present a penetration depth of about 0.9,nm, which is much smaller than those predicted in other 2D topological systems. Thus, suggesting that Pt2HgSe3 allows the exploitation of topological transport properties in narrow ribbons. Using non-equilibrium Green's functions calculations, we have examined the electron conductivity upon the presence of Se,↔,Hg antistructure defects randomly distributed in the Pt2HgSe3 scattering region. By considering scattering lengths up to 109,nm, we found localization lengths that can surpass μm sizes for narrow nanoribbons (<9,nm). These findings can contribute to further understanding the behavior of topological insulators under realistic conditions and their integration within electronic, spintronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
The discovery of the quantum spin Hall effect led to the exploration of the electronic transport for spintronic devices. Here, we theoretically investigated the electronic conductance in large-gap realistic quantum spin Hall system, Pt2HgSe3 nanoribbons. By an ab initio approach, we found that the edge states present a penetration depth of about 0.9,nm, which is much smaller than those predicted in other 2D topological systems. Thus, suggesting that Pt2HgSe3 allows the exploitation of topological transport properties in narrow ribbons. Using non-equilibrium Green's functions calculations, we have examined the electron conductivity upon the presence of Se,↔,Hg antistructure defects randomly distributed in the Pt2HgSe3 scattering region. By considering scattering lengths up to 109,nm, we found localization lengths that can surpass μm sizes for narrow nanoribbons (<9,nm). These findings can contribute to further understanding the behavior of topological insulators under realistic conditions and their integration within electronic, spintronic devices.
2023
Araújo, A. L.; Lima, F. Crasto; Lewenkopf, C. H.; Fazzio, Adalberto
Design of spin-orbital-textures in ferromagnetic/topological insulator interfaces Working paper
2023.
@workingpaper{araújo2023design,
title = {Design of spin-orbital-textures in ferromagnetic/topological insulator interfaces},
author = {A. L. Araújo and F. Crasto Lima and C. H. Lewenkopf and Adalberto Fazzio},
url = {https://arxiv.org/abs/2311.11084},
doi = {https://doi.org/10.48550/arXiv.2311.11084},
year = {2023},
date = {2023-11-18},
urldate = {2023-11-18},
abstract = {Spin-orbital textures in topological insulators due to the spin locking with the electron momentum, play an important role in spintronic phenomena that arise from the interplay between charge and spin degrees of freedom. We have explored interfaces between a ferromagnetic system (CrI3) and a topological insulator (Bi2Se3) that allow the manipulation of spin-orbital textures. Within an it ab initio approach we have extracted the spin-orbital-textures dependence of experimentally achievable interface designs. The presence of the ferromagnetic system introduces anisotropic transport of the electronic spin and charge. From a parameterized Hamiltonian model we capture the anisotropic backscattering behavior, showing its extension to other ferromagnetic/topological insulator interfaces. We verified that the van der Waals TI/MI interface is an excellent platform for controlling the spin degree of freedom arising from topological states, providing a rich family of unconventional spin texture configurations.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
Spin-orbital textures in topological insulators due to the spin locking with the electron momentum, play an important role in spintronic phenomena that arise from the interplay between charge and spin degrees of freedom. We have explored interfaces between a ferromagnetic system (CrI3) and a topological insulator (Bi2Se3) that allow the manipulation of spin-orbital textures. Within an it ab initio approach we have extracted the spin-orbital-textures dependence of experimentally achievable interface designs. The presence of the ferromagnetic system introduces anisotropic transport of the electronic spin and charge. From a parameterized Hamiltonian model we capture the anisotropic backscattering behavior, showing its extension to other ferromagnetic/topological insulator interfaces. We verified that the van der Waals TI/MI interface is an excellent platform for controlling the spin degree of freedom arising from topological states, providing a rich family of unconventional spin texture configurations.
Pezo, Armando; Lima, F. Crasto; Fazzio, Adalberto
Electronic and spin transport in Bismuthene with magnetic impurities Working paper
2023.
@workingpaper{pezo2023electronic,
title = {Electronic and spin transport in Bismuthene with magnetic impurities},
author = {Armando Pezo and F. Crasto Lima and Adalberto Fazzio},
url = {https://arxiv.org/abs/2309.07328},
doi = {https://doi.org/10.48550/arXiv.2309.07328},
year = {2023},
date = {2023-09-13},
urldate = {2023-01-01},
abstract = {Topological insulators have remained as candidates for future electronic devices since their first experimental realization in the past decade. The existence of topologically protected edge states could be exploited to generate a robust platform and develop quantum computers. In this work we explore the role of magnetic impurities in the transport properties of topological insulators, in particular, we study the effect on the edge states conductivity. By means of realistic ab initio calculations we simulate the interaction between magnetic adatoms and topological insulators, furthermore, our main goal is to obtain the transport properties for large samples as it would be possible to localize edge states at large scales.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
Topological insulators have remained as candidates for future electronic devices since their first experimental realization in the past decade. The existence of topologically protected edge states could be exploited to generate a robust platform and develop quantum computers. In this work we explore the role of magnetic impurities in the transport properties of topological insulators, in particular, we study the effect on the edge states conductivity. By means of realistic ab initio calculations we simulate the interaction between magnetic adatoms and topological insulators, furthermore, our main goal is to obtain the transport properties for large samples as it would be possible to localize edge states at large scales.
Lima, F. Crasto; Focassio, B; Miwa, Roberto H.; Fazzio, Adalberto
Topological insulating phase arising in transition metal dichalcogenide alloy Journal Article
Em: 2D Materials, vol. 10, não 3, pp. 035001, 2023.
@article{CrastodeLima_2023,
title = {Topological insulating phase arising in transition metal dichalcogenide alloy},
author = {F. Crasto Lima and B Focassio and Roberto H. Miwa and Adalberto Fazzio},
url = {https://dx.doi.org/10.1088/2053-1583/acc670},
doi = {10.1088/2053-1583/acc670},
year = {2023},
date = {2023-04-01},
urldate = {2023-04-01},
journal = {2D Materials},
volume = {10},
number = {3},
pages = {035001},
publisher = {IOP Publishing},
abstract = {Transition metal dichalcogenides have been the subject of numerous studies addressing technological applications and fundamental issues. Single-layer PtSe2 is a semiconductor with a trivial bandgap, in contrast, its counterpart with of Se atoms substituted by Hg, Pt2HgSe3 (jacutingaite, a naturally occurring mineral) is a 2D topological insulator with a large bandgap. Based on ab-initio calculations, we investigate the energetic stability, and the topological transition in Pt(Hg x Se)2 as a function of alloy concentration, and the distribution of Hg atoms embedded in the PtSe2 host. Our findings reveal the dependence of the topological phase with respect to the alloy concentration and robustness with respect to the distribution of Hg. Through a combination of our ab-initio results and a defect wave function percolation model, we estimate the random alloy concentration threshold for the topological transition to be only . Our results expand the possible search for non-trivial topological phases in random alloy systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Transition metal dichalcogenides have been the subject of numerous studies addressing technological applications and fundamental issues. Single-layer PtSe2 is a semiconductor with a trivial bandgap, in contrast, its counterpart with of Se atoms substituted by Hg, Pt2HgSe3 (jacutingaite, a naturally occurring mineral) is a 2D topological insulator with a large bandgap. Based on ab-initio calculations, we investigate the energetic stability, and the topological transition in Pt(Hg x Se)2 as a function of alloy concentration, and the distribution of Hg atoms embedded in the PtSe2 host. Our findings reveal the dependence of the topological phase with respect to the alloy concentration and robustness with respect to the distribution of Hg. Through a combination of our ab-initio results and a defect wave function percolation model, we estimate the random alloy concentration threshold for the topological transition to be only . Our results expand the possible search for non-trivial topological phases in random alloy systems.
Silvestre, G. H.; Lima, F. Crasto; Bernardes, J. S.; Fazzio, Adalberto; Miwa, Roberto H.
Nanoscale structural and electronic properties of cellulose/graphene interfaces Journal Article
Em: Phys. Chem. Chem. Phys., vol. 25, não 2, pp. 1161–1168, 2023, ISSN: 1463-9084.
@article{Silvestre2023,
title = {Nanoscale structural and electronic properties of cellulose/graphene interfaces},
author = {G. H. Silvestre and F. Crasto Lima and J. S. Bernardes and Adalberto Fazzio and Roberto H. Miwa},
doi = {10.1039/d2cp04146d},
issn = {1463-9084},
year = {2023},
date = {2023-01-04},
urldate = {2023-01-04},
journal = {Phys. Chem. Chem. Phys.},
volume = {25},
number = {2},
pages = {1161–1168},
publisher = {Royal Society of Chemistry (RSC)},
abstract = {<jats:p>The development of electronic devices based on the functionalization of (nano)cellulose platforms relies upon an atomistic understanding of the structural and electronic properties of a combined system, cellulose/functional element.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>The development of electronic devices based on the functionalization of (nano)cellulose platforms relies upon an atomistic understanding of the structural and electronic properties of a combined system, cellulose/functional element.</jats:p>
Okazaki, Anderson K.; Oliveira, Rafael Furlan; Freire, Rafael Luiz Heleno; Fazzio, Adalberto; Lima, F. Crasto
Uncovering the Structural Evolution of Arsenene on SiC Substrate Journal Article
Em: The Journal of Physical Chemistry C, vol. 127, não 16, pp. 7894-7899, 2023.
@article{doi:10.1021/acs.jpcc.3c00938,
title = {Uncovering the Structural Evolution of Arsenene on SiC Substrate},
author = {Anderson K. Okazaki and Rafael Furlan Oliveira and Rafael Luiz Heleno Freire and Adalberto Fazzio and F. Crasto Lima},
url = {https://doi.org/10.1021/acs.jpcc.3c00938},
doi = {10.1021/acs.jpcc.3c00938},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {The Journal of Physical Chemistry C},
volume = {127},
number = {16},
pages = {7894-7899},
abstract = {Two-dimensional arsenic allotropes have been grown on metallic surfaces, while topological properties have been theoretically described on strained structures. Here, we experimentally grow arsenene by molecular beam epitaxy over the insulating SiC substrate. The arsenene presents a flat structure with a strain field that follows the SiC surface periodicity. Our ab initio simulations, based on the density functional theory, corroborate the experimental observation. The strained structure presents a new arsenene allotrope with a triangular structure, rather than the honeycomb previously predicted for other pnictogens. This strained structure presents a Peierls-like transition leading to an indirect gap semiconducting behavior.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional arsenic allotropes have been grown on metallic surfaces, while topological properties have been theoretically described on strained structures. Here, we experimentally grow arsenene by molecular beam epitaxy over the insulating SiC substrate. The arsenene presents a flat structure with a strain field that follows the SiC surface periodicity. Our ab initio simulations, based on the density functional theory, corroborate the experimental observation. The strained structure presents a new arsenene allotrope with a triangular structure, rather than the honeycomb previously predicted for other pnictogens. This strained structure presents a Peierls-like transition leading to an indirect gap semiconducting behavior.
Freire, R. L. H.; Lima, F. Crasto; Fazzio, Adalberto
Substrate suppression of oxidation process in pnictogen monolayers Working paper
2023.
@workingpaper{freire2023substrate,
title = {Substrate suppression of oxidation process in pnictogen monolayers},
author = {R. L. H. Freire and F. Crasto Lima and Adalberto Fazzio},
url = {https://arxiv.org/abs/2307.00138},
doi = {10.48550/arXiv.2307.00138},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
abstract = {2D materials present an interesting platform for device designs. However, oxidation can drastically change the system's properties, which need to be accounted for. Through it ab initio calculations, we investigated freestanding and SiC-supported As, Sb, and Bi mono-elemental layers. The oxidation process occurs through an O2 spin-state transition, accounted for within the Landau-Zener transition. Additionally, we have investigated the oxidation barriers and the role of spin-orbit coupling. Our calculations pointed out that the presence of SiC substrate reduces the oxidation time scale compared to a freestanding monolayer. We have extracted the energy barrier transition, compatible with our spin-transition analysis. Besides, spin-orbit coupling is relevant to the oxidation mechanisms and alters time scales. The energy barriers decrease as the pnictogen changes from As to Sb to Bi for the freestanding systems, while for SiC-supported, they increase across the pnictogen family. Our computed energy barriers confirm the enhanced robustness against oxidation for the SiC-supported systems.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
2D materials present an interesting platform for device designs. However, oxidation can drastically change the system's properties, which need to be accounted for. Through it ab initio calculations, we investigated freestanding and SiC-supported As, Sb, and Bi mono-elemental layers. The oxidation process occurs through an O2 spin-state transition, accounted for within the Landau-Zener transition. Additionally, we have investigated the oxidation barriers and the role of spin-orbit coupling. Our calculations pointed out that the presence of SiC substrate reduces the oxidation time scale compared to a freestanding monolayer. We have extracted the energy barrier transition, compatible with our spin-transition analysis. Besides, spin-orbit coupling is relevant to the oxidation mechanisms and alters time scales. The energy barriers decrease as the pnictogen changes from As to Sb to Bi for the freestanding systems, while for SiC-supported, they increase across the pnictogen family. Our computed energy barriers confirm the enhanced robustness against oxidation for the SiC-supported systems.
Scopel, Wanderlã L.; Lima, F. Crasto; Souza, Pedro H.; Padilha, José E.; Miwa, Roberto H.
Bridging Borophene and Metal Surfaces: Structural, Electronic, and Electron Transport Properties Journal Article
Em: The Journal of Physical Chemistry C, vol. 127, não 35, pp. 17556-17566, 2023.
@article{doi:10.1021/acs.jpcc.3c03123,
title = {Bridging Borophene and Metal Surfaces: Structural, Electronic, and Electron Transport Properties},
author = {Wanderlã L. Scopel and F. Crasto Lima and Pedro H. Souza and José E. Padilha and Roberto H. Miwa},
url = {https://doi.org/10.1021/acs.jpcc.3c03123},
doi = {10.1021/acs.jpcc.3c03123},
year = {2023},
date = {2023-01-01},
journal = {The Journal of Physical Chemistry C},
volume = {127},
number = {35},
pages = {17556-17566},
abstract = {Currently, solid interfaces composed of two-dimensional materials (2D) in contact with metal surfaces (m-surf) have been the subject of intense research, where the borophene bilayer (BBL) has been considered a prominent material for the development of electronic devices based on 2D platforms. In this work, we present a theoretical study of the energetic, structural, and electronic properties of the BBL/m-surf interface, with m-surf = Ag(111), Au(111), and Al(111) surfaces, and the electronic transport properties of BBL channels connected to the BBL/m-surf top contacts. We find that the BBL becomes metallized due to hybridization with the metal surface states, resulting in Ohmic contacts between BBL and m-surf. However, the projected wavefunctions indicate that the inner and top-most boron layers have a weaker interaction with the m-surf, thus retaining their semiconducting character. The net charge transfers reveal that BBL has become n-type (p-type) doped for m-surf = Ag and Al (= Au). A thorough structural characterization of the BBL/m-surf interface, using a series of simulations of X-ray photoelectron spectra, shows that the formation of the BBL/m-surf interface is characterized by a red shift of the B-1s spectra. Further electronic transport results revealed the emergence of a Schottky barrier between 0.1 and 0.2 eV between the BBL/m-surf contact and the BBL channels. We believe that our findings are timely, bringing important contributions to the applicability of BBLs for developing 2D electronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Currently, solid interfaces composed of two-dimensional materials (2D) in contact with metal surfaces (m-surf) have been the subject of intense research, where the borophene bilayer (BBL) has been considered a prominent material for the development of electronic devices based on 2D platforms. In this work, we present a theoretical study of the energetic, structural, and electronic properties of the BBL/m-surf interface, with m-surf = Ag(111), Au(111), and Al(111) surfaces, and the electronic transport properties of BBL channels connected to the BBL/m-surf top contacts. We find that the BBL becomes metallized due to hybridization with the metal surface states, resulting in Ohmic contacts between BBL and m-surf. However, the projected wavefunctions indicate that the inner and top-most boron layers have a weaker interaction with the m-surf, thus retaining their semiconducting character. The net charge transfers reveal that BBL has become n-type (p-type) doped for m-surf = Ag and Al (= Au). A thorough structural characterization of the BBL/m-surf interface, using a series of simulations of X-ray photoelectron spectra, shows that the formation of the BBL/m-surf interface is characterized by a red shift of the B-1s spectra. Further electronic transport results revealed the emergence of a Schottky barrier between 0.1 and 0.2 eV between the BBL/m-surf contact and the BBL channels. We believe that our findings are timely, bringing important contributions to the applicability of BBLs for developing 2D electronic devices.