Examinando por Autor "Woods, Lilia M."

Mostrando 1 - 9 de 9

Casimir force phase transitions in the graphene family
(Springer Nature, 2017-03-15) Rodriguez-Lopez, Pablo; Kort-Kamp, Wilton J.M.; Dalvit, Diego A.R.; Woods, Lilia M.
The Casimir force is a universal interaction induced by electromagnetic quantum fluctuations between any types of objects. The expansion of the graphene family by adding silicene, germanene and stanene (2D allotropes of Si, Ge, and Sn), lends itself as a platform to probe Dirac-like physics in honeycomb staggered systems in such a ubiquitous interaction. We discover Casimir force phase transitions between these staggered 2D materials induced by the complex interplay between Dirac physics, spin-orbit coupling and externally applied fields. In particular, we find that the interaction energy experiences different power law distance decays, magnitudes and dependences on characteristic physical constants. Furthermore, due to the topological properties of these materials, repulsive and quantized Casimir interactions become possible.
Confinement-Induced Nonlocality and Casimir Force in Transdimensional Systems
(The Royal Society of Chemistry, 2023-10-09) Bondarev, Igor V.; Pugh, Michael D.; Rodriguez-Lopez, Pablo; Woods, Lilia M.; Antezza, Mauro
We study within the framework of the Lifshitz theory the long-range Casimir force for in-plane isotropic and anisotropic free-standing transdimensional material slabs. In the former case{,} we show that the confinement-induced nonlocality not only weakens the attraction of ultrathin slabs but also changes the distance dependence of the material-dependent correction to the Casimir force to go as contrary to the ∼1/l dependence of that of the local Lifshitz force. In the latter case{,} we use closely packed array of parallel aligned single-wall carbon nanotubes in a dielectric layer of finite thickness to demonstrate strong orientational anisotropy and crossover behavior for the inter-slab attractive force in addition to its reduction with decreasing slab thickness. We give physical insight as to why such a pair of ultrathin slabs prefers to stick together in the perpendicularly oriented manner{,} rather than in the parallel relative orientation as one would customarily expect.
Contemporary Quantum Mechanics in Practice: Problems and Solutions
(Cambridge University Press, 2024-06) Woods, Lilia M.; Rodríguez López, Pablo
This helpful and pedagogical book offers problems and solutions in quantum mechanics from areas of current research, rarely addressed in introductory courses or textbooks. It is based on the authors' own experience of teaching undergraduate and graduate courses in quantum mechanics, and adapts problems from contemporary research publications to be accessible to students. Each section introduces key quantum mechanical concepts, which are followed by exercises that grow progressively more challenging throughout the chapter. The step-by-step solutions provide detailed mathematical derivations, and explore their application to wider research topics. This is an indispensable resource for undergraduate and graduate students alike, expanding the range of topics usually covered in the classroom, as well as for instructors and early-career researchers in quantum mechanics, quantum computation and communication, and quantum information.
Giant anisotropy and Casimir phenomena: The case of carbon nanotube metasurfaces
(American Physical Society, 2024-01-17) Rodriguez-Lopez, Pablo; Le, Dai-Nam; Bondarev, Igor V.; Antezza, Mauro; Woods, Lilia M.
The Casimir interaction and torque are related phenomena originating from the exchange of electromagnetic excitations between objects. While the Casimir force exists between any types of objects, the materials or geometrical anisotropy drives the emergence of the Casimir torque. Here both phenomena are studied theoretically between dielectric films with immersed parallel single wall carbon nanotubes in the dilute limit with their chirality and collective electronic and optical response properties taken into account. It is found that the Casimir interaction is dominated by thermal fluctuations at sub-micron separations, while the torque is primarily determined by quantum mechanical effects. This peculiar quantum vs. thermal separation is attributed to the strong influence of reduced dimensionality and inherent anisotropy of the materials. Our study suggests that nanostructured anisotropic materials can serve as novel platforms to uncover new functionalities in ubiquitous Casimir phenomena.
Materials perspective on Casimir and van der Waals interactions
(American Physical Society, 2016-11-02) Woods, Lilia M.; Dalvit, Diego A. R.; Tkatchenko, Alexandre; Rodriguez-Lopez, Pablo; Rodriguez, Alejandro W.; Podgornik, Rudolf
Interactions induced by electromagnetic fluctuations, such as van der Waals and Casimir forces, are of universal nature present at any length scale between any types of systems. Such interactions are important not only for the fundamental science of materials behavior, but also for the design and improvement of micro- and nanostructured devices. In the past decade, many new materials have become available, which has stimulated the need for understanding their dispersive interactions. The field of van der Waals and Casimir forces has experienced an impetus in terms of developing novel theoretical and computational methods to provide new insights into related phenomena. The understanding of such forces has far reaching consequences as it bridges concepts in materials, atomic and molecular physics, condensed-matter physics, high-energy physics, chemistry, and biology. This review summarizes major breakthroughs and emphasizes the common origin of van der Waals and Casimir interactions. Progress related to novel ab initio modeling approaches and their application in various systems, interactions in materials with Dirac-like spectra, force manipulations through nontrivial boundary conditions, and applications of van der Waals forces in organic and biological matter are examined. The outlook of the review is to give the scientific community a materials perspective of van der Waals and Casimir phenomena and stimulate the development of experimental techniques and applications.
Nonlocal optical response in topological phase transitions in the graphene family
(American Physical Society, 2018-01-22) Rodriguez-Lopez, Pablo; Kort-Kamp, Wilton J. M.; Dalvit, Diego A. R.; Woods, Lilia M.
We investigate the electromagnetic response of staggered two-dimensional materials of the graphene family, including silicene, germanene, and stanene, as they are driven through various topological phase transitions using external fields. Utilizing Kubo formalism, we compute their optical conductivity tensor taking into account the frequency and wave vector of the electromagnetic excitations, and study its behavior over the full electronic phase diagram of the materials. In particular, we find that the resonant behavior of the nonlocal Hall conductivity is strongly affected by the various topological phases present in these materials. We also consider the plasmon excitations in the graphene family and find that nonlocality in the optical response can affect the plasmon dispersion spectra of the various phases. We find a regime of wave vectors for which the plasmon relations for phases with trivial topology are essentially indistinguishable, while those for phases with nontrivial topology are distinct and are redshifted as the corresponding Chern number increases. The expressions for the conductivity components are valid for the entire graphene family and can be readily used by others.
Phonon-assisted Casimir interactions between piezoelectric materials
(Nature Portfolio, 2024-12-02) Le, Dai-Nam; Rodriguez-Lopez, Pablo; Woods, Lilia M.
The strong coupling between electromagnetic fields and lattice oscillations in piezoelectric materials gives rise to phonon polariton excitations. Such quasiparticles are important in modulating the ubiquitous Casimir force. Here by utilizing the generalized Born-Huang hydrodynamics model exemplified in SiC, three types of phonons are studied: longitudinal optical phonon, transverse optical phonon and phonon polariton. The Fresnel reflection coefficients for the piezoelectric composed of semi-infinite substrates or thin films are then obtained by taking into account the phonon-electromagnetic coupling. The Casimir interaction, calculated via a generalized Lifshitz approach, is examined to highlight the interplay between different types of phonon modes and electromagnetic excitations. Our study shows that piezoelectrics emerge as materials where this ubiquitous force can be controlled via phonon properties. Different types of surface phonon polaritons associated with structural polytypes may also be distinguished through the Casimir interaction.
Thermally driven anomalous Hall effect transitions in FeRh
(American Physical Society, 2018-04-30) Popescu, Adrian; Rodriguez-Lopez, Pablo; Haney, Paul M.; Woods, Lilia M.
Materials exhibiting controllable magnetic phase transitions are currently in demand for many spintronics applications. Here, we investigate from first principles the electronic structure and intrinsic anomalous Hall, spin Hall, and anomalous Nernst response properties of the FeRh metallic alloy which undergoes a thermally driven antiferromagnetic-to-ferromagnetic phase transition. We show that the energy band structures and underlying Berry curvatures have important signatures in the various Hall effects. Specifically, the suppression of the anomalous Hall and Nernst effects in the antiferromagnetic state and a sign change in the spin Hall conductivity across the transition are found. It is suggested that the FeRh can be used as a spin current detector capable of differentiating the spin Hall effect from other anomalous transverse effects. The implications of this material and its thermally driven phases as a spin current detection scheme are also discussed.
Twisted bilayered graphenes at magic angles and Casimir interactions: correlation-driven effects
(IOP Publishing, 2022-10-27) Rodriguez-Lopez, Pablo; Le, Dai-Nam; Calderón, María José; Bascones, Elena; Woods, Lilia M.
Twisted bilayered graphenes (TBGs) at magic angles are systems housing long ranged periodicity of moiré patterns together with short ranged periodicity associated with the individual graphenes. Such materials are a fertile ground for novel states largely driven by electronic correlations. Here we find that the ubiquitous Casimir force can serve as a platform for macroscopic manifestations of the quantum effects stemming from the magic angle bilayered graphenes properties and their phases determined by electronic correlations. By utilizing comprehensive calculations for the electronic and optical response, we find that Casimir torque can probe anisotropy from the Drude conductivities in nematic states, while repulsion in the Casimir force can help identify topologically nontrivial phases in magic angle TBGs.