Prof. Gerardo G Naumis

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Academic Career Length

34Years (1993-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 August 2017 in Reports on Progress in Physics

Journal Article

Electronic and optical properties of strained graphene and other strained 2D materials: a review

Gerardo G Naumis

Salvador Barraza-Lopez

Maurice Oliva-Leyva

Humberto Terrones

This review presents the state of the art in strain and ripple-induced effects on the electronic and optical properties of graphene. It starts by providing the crystallographic description of mechanical deformations, as well as the diffraction pattern for different kinds of representative deformation fields. Then, the focus turns to the unique elastic properties of graphene, and to how strain is produced. Thereafter, various theoretical approaches used to study the electronic properties of strained graphene are examined, discussing the advantages of each. These approaches provide a platform to describe exotic properties, such as a fractal spectrum related with quasicrystals, a mixed Dirac–Schrödinger behavior, emergent gravity, topological insulator states, in molecular graphene and other 2D discrete lattices. The physical consequences of strain on the optical properties are reviewed next, with a focus on the Raman spectrum. At the same time, recent advances to tune the optical conductivity of graphene by strain engineering are given, which open new paths in device applications. Finally, a brief review of strain effects in multilayered graphene and other promising 2D materials like silicene and materials based on other group-IV elements, phosphorene, dichalcogenide- and monochalcogenide-monolayers is presented, with a brief discussion of interplays among strain, thermal effects, and illumination in the latter material family.

26 August 2013 in Physical Review B

Journal Article

Understanding electron behavior in strained graphene as a reciprocal space distortion

M. Oliva-Leyva

Gerardo G Naumis

The behavior of electrons in strained graphene is usually described using effective pseudomagnetic fields in a Dirac equation. Here we consider the particular case of a spatially constant strain. Our results indicate that lattice corrections are easily understood using a strained reciprocal space, in which the whole energy dispersion is simply shifted and deformed. This leads to a directional-dependent Fermi velocity without producing pseudomagnetic fields. The corrections due to atomic wave function overlap changes tend to compensate such effects. Also, the analytical expressions for the shift of the Dirac points, which do not coincide with the

K

points of the renormalized reciprocal lattice, as well as the corresponding Dirac equation are found. In view of the former results, we discuss the range of applicability of the usual approach of considering pseudomagnetic fields in a Dirac equation derived from the old Dirac points of the unstrained lattice or around the

K

points of the renormalized reciprocal lattice. Such considerations are important if a comparison is desired with experiments or numerical simulations.

1 October 2015 in Physics Letters A

Journal Article

Generalizing the Fermi velocity of strained graphene from uniform to nonuniform strain

M. Oliva-Leyva

Gerardo G Naumis

14 February 2005 in Physical Review E

Journal Article

Energy landscape and rigidity

Gerardo G Naumis

The effects of floppy modes in the thermodynamical properties of a system are studied. From thermodynamical arguments, we deduce that floppy modes are not at zero frequency and thus a modified Debye model is used to take into account this effect. The model predicts a deviation from the Debye law at low temperatures. Then, the connection between the topography of the energy landscape, the topology of the phase space, and the rigidity of a glass is explored. As a result, we relate the number of constraints and floppy modes to the statistics of the landscape. We apply these ideas to a simple model for which we provide an approximate expression for the number of energy basins as a function of the rigidity. This helps to understand certain features of the glass transition, like the jump in the specific heat or the reversible window observed in chalcogenide glasses.

17 November 2008 in Physical Review B

Journal Article

Analytic solution for electrons and holes in graphene under electromagnetic waves: Gap appearance and nonlinear effects

F. J. López-Rodríguez

Gerardo G Naumis

We find the exact solution of graphene carriers dynamics under electromagnetic radiation. To obtain the solution of the corresponding Dirac equation, we combine Floquet theory with a trial solution. Then the energy spectrum is obtained without using any approximation. We also prove that the energy spectrum presents a gap opening, which depends on the radiation frequency and electric wave intensity, whereas the current shows a strongly nonlinear behavior.

7 January 2019 in Physical Review B

Journal Article

Valley engineering by strain in Kekulé-distorted graphene

Elias Andrade

Ramon Carrillo-Bastos

Gerardo G Naumis

A Kekulé bond texture in graphene modifies the electronic band structure by folding the Brillouin zone and bringing the two inequivalent Dirac points to the center. This can result in the opening of a gap (Kek-O) or the locking of the valley degree of freedom with the direction of motion (Kek-Y). We analyze the effects of uniaxial strain on the band structure of Kekulé-distorted graphene for both textures. Using a tight-binding approach, we introduce strain by considering the hopping renormalization and corresponding geometrical modifications of the Brillouin zone. We numerically evaluate the dispersion relation and present analytical expressions for the low-energy limit. Our results indicate the emergence of a Zeeman-like term due to the coupling of the pseudospin with the pseudomagnetic strain potential which separates the valleys by moving them in opposite directions away from the center of the Brillouin zone. For the Kek-O phase, this results in a competition between the Kekulé parameter that opens a gap and the magnitude of strain which closes it, while for the Kek-Y phase, it results in a superposition of two shifted Dirac cones. As the Dirac cones are much closer in the superlattice reciprocal space than in pristine graphene, we propose strain as a control parameter for intervalley scattering.

About Me

Gerardo G. Naumis studied physics at the Mexico National University (UNAM) and earned his Ph.D. at the same institution. In 1998, he completed a postdoc at Paris VI University with Prof. Richard Kerner, and since 1998, he has worked at the Physics Institute of the Mexico National University (UNAM) in Mexico City. He is the author of more than 160 scientific papers and 14 book chapters concerning many different topics, such as solid-state physics, materials science, complex systems, fluids, soft matter, biology, statistical mechanics, quantum systems and meteorology. He has been an invited professor in the USA, France, Spain, England, Portugal and Brazil and appointed associate editor of the journal Frontiers in Materials edited by the Nature group in England. He won the prizes Jóvenes Investigadores en Ciencias Exactas (UNAM), Premio Ciudad Capital Heberto Castillo (CDMX government) for Young scientists, Jorge Lomnitz Prize of the Academia Mexicana de Ciencias for his contributions in complex systems and non-linear science, Premio Marcos Moshinsky for outstanding contributions in theoretical physics, and the Quo-Discovery Channel prize and was designated a distinguished professor at the Universidad Iberoamericana. He was considered by Time Mexico in 2005 among one of the 100 young leaders in Mexico. His students have won the Weizmann Prize, given by the Mexican Academy of Sciences for the best Ph.D. thesis in Mexico concerning exact sciences, three times.

Prof. Gerardo G Naumis

Prof. Gerardo G Naumis

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