Examinando por Autor "Urrutia, L.F."

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    Electromagnetic description of three-dimensional time-reversal invariant ponderable topological insulators
    (American Physical Society, 2016-10) Martín-Ruiz, A.; Cambiaso, M.; Urrutia, L.F.
    A general technique to analyze the classical interaction between ideal topological insulators, and electromagnetic sources and fields, has been previously elaborated. Nevertheless it is not immediately applicable in the laboratory as it fails to describe real ponderable media. In this work we provide a description of real topologically insulating materials taking into account their dielectric and magnetic properties. For inhomogeneous permittivity and permeability, the problem of finding the Green’s function must be solved in an ad hoc manner. Nevertheless, the physically feasible cases of piecewise constant ε, μ and θ make the problem tractable, where θ encodes the topological magnetoelectric polarizability properties of the medium. To this end we employ the Green’s function method to find the fields resulting from the interaction between these materials and electromagnetic sources. Furthermore we exploit the fact that in the cases here studied, the full Green’s function can be successfully found if the Green’s function of the corresponding ponderable media with θ ¼ 0 is known. Our results satisfactorily reproduce previously existing ones and also generalize some others. The method here elaborated can be exploited to determine the electromagnetic fields for more general configurations aiming to measure the interaction between real 3D topological insulators and electromagnetic fields.
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    Green's function approach to Chern-Simons extended electrodynamics: An effective theory describing topological insulators
    (American Physical Society, 2015-12) Martín-Ruiz, A.; Cambiaso, M.; Urrutia, L.F.
    Boundary effects produced by a Chern-Simons (CS) extension to electrodynamics are analyzed exploiting the Green's function (GF) method. We consider the electromagnetic field coupled to a. term in a way that has been proposed to provide the correct low-energy effective action for topological insulators (TI). We take the theta term to be piecewise constant in different regions of space separated by a common interface Sigma, which will be called the theta boundary. Features arising due to the presence of the boundary, such as magnetoelectric effects, are already known in CS extended electrodynamics, and solutions for some experimental setups have been found, each with its specific configuration of sources. In this work we illustrate a method to construct the GF that allows us to solve the CS modified field equations for a given. boundary with otherwise arbitrary configuration of sources. The method is illustrated by solving the case of a planar. boundary but can also be applied for cylindrical and spherical geometries for which the theta boundary can be characterized by a surface where a given coordinate remains constant. The static fields of a pointlike charge interacting with a planar TI, as described by a planar discontinuity in theta, are calculated and successfully compared with previously reported results. We also compute the force between the charge and the. boundary by two different methods, using the energy-momentum tensor approach and the interaction energy calculated via the GF. The infinitely straight current-carrying wire is also analyzed.
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    The magnetoelectric coupling in electrodynamics
    (World Scientific Publishing Co. Pte Ltd, 2019-11) Martín-Ruiz A.; Cambiaso, M.; Urrutia, L.F.
    We explore a model akin to axion electrodynamics in which the axion field (t,x) rather than being dynamical is a piecewise constant effective parameter encoding the microscopic properties of the medium inasmuch as its permittivity or permeability, defining what we call a-medium. This model describes a large class of phenomena, among which we highlight the electromagnetic response of materials with topological order, like topological insulators for example. We pursue a Green's function formulation of what amounts to typical boundary-value problems of-media, when external sources or boundary conditions are given. As an illustration of our methods, which we have also extended to ponderable media, we interpret the constant as a novel topological property of vacuum, a so called-vacuum, and restrict our discussion to the cases where the permittivity and the permeability of the media is one. In this way we concentrate upon the effects of the additional coupling which induce remarkable magnetoelectric effects. The issue of boundary conditions for electromagnetic radiation is crucial for the occurrence of the Casimir effect, therefore we apply the methods described above as an alternative way to approach the modifications to the Casimir effect by the inclusion of topological insulators. © 2019 World Scientific Publishing Company.