Examinando por Autor "Woods, Lilia M"

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Composition and stacking dependent topology in bilayers from the graphene family
(American Physical Society, 2019-06-21) Popescu, Adrian; Rodriguez-Lopez, Pablo; Woods, Lilia M
We present a compositional and structural investigation of silicene, germanene, and stanene bilayers from first principles. Due to the staggering of the individual layers, several stacking patterns are possible, most of which are not available to the bilayer graphene. This structural variety, in conjunction with the presence of the spin-orbit coupling, unveils a diversity of the electronic properties, with the appearance of distinct band features, including orbital hybridization and band inversion. We show that for particular cases, the intrinsic spin Hall response exhibits signatures of nontrivial electronic band topology, making these structures promising candidates to probe Dirac-like physics.
Dispersive interactions between standard and Dirac materials and the role of dimensionality
(IOP Publishing, 2022-05-17) Le, Dai-Nam; Rodriguez-Lopez, Pablo; Woods, Lilia M
The van der Waals (vdW) interaction plays a prominent role between neutral objects at separations where short ranged chemical forces are negligible. This type of dispersive coupling is determined by the interplay between geometry and response properties of the materials making up the objects. Here, we investigate the vdW interaction between 1D, 2D, and 3D standard and Dirac materials within the Random Phase Approximation, which takes into account collective excitations originating from the electronic Coulomb potential. A comprehensive understanding of characteristic functionalities and scaling laws are obtained for systems with parabolic energy dispersion (standard materials) and crossing linear bands (Dirac materials). By comparing the quantum mechanical and thermal limits the onset of thermal fluctuations in the vdW interaction is discussed showing that thermal effects are significantly pronounced at smaller scales in reduced dimensions.
Nonlinear effects in manybody van der Waals interactions
(American Physical Society, 2024-03-15) Le, Dai-Nam; Rodriguez-Lopez, Pablo; Woods, Lilia M
Van der Waals interactions are ubiquitous and they play an important role for the stability of materials. Current understanding of this type of coupling is based on linear response theory, while optical nonlinearities are rarely considered in this context. Many materials, however, exhibit strong optical nonlinear response, which prompts further evaluation of dispersive forces beyond linear response. Here we present a discrete coupled nonlinear dipole approach that takes into account linear and nonlinear properties of all dipolar nanoparticles in a given system. This method is based on a Hamiltonian for nonlinear dipoles, which we apply in different systems uncovering a complex interplay of distance, anisotropy, polarizabilities, and hyperpolarizabilities in the vdW energy. This investigation broadens our basic understanding of dispersive interactions, especially in the context of nonlinear materials.
Signatures of complex optical response in Casimir interactions of type I and II Weyl semimetals
(Nature Portfolio, 2020-03-26) Rodriguez-Lopez, Pablo; Popescu, Adrian; Fialkovsky, Ignat; Khusnutdinov, Nail; Woods, Lilia M
The Casimir interaction, induced by electromagnetic fluctuations between objects, is strongly dependent upon the electronic and optical properties of the materials making up the objects. Here we investigate this ubiquitous interaction between semi-infinite spaces of topologically nontrivial Weyl semimetals. A comprehensive examination of all components of the bulk conductivity tensor and the surface conductivity due to the Fermi arc states in real and imaginary frequency domains is presented using the Kubo formalism for materials with different degree of tilting of their linear energy cones. The Casimir energy is calculated using a generalized Lifshitz approach, for which electromagnetic boundary conditions for anisotropic materials were derived and used. We find that the interaction between Weyl semimetals is metallic-like and its magnitude and characteristic distance dependence can be modified by the degree of tilting and chemical potential. The nontrivial topology plays a secondary role in the interaction and thermal fluctuations are expected to have similar effects as in metallic systems.