Surface Waves at the Interface between a Dielectric and a Topological Insulator (original) (raw)
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Guided Electromagnetic Waves at the Interface between a Dielectric and a Topological Insulator
Bulletin of the Russian Academy of Sciences: Physics, 2018
Surface electromagnetic waves that propagate within the interface between a conventional dielec-tric or a metamaterial and a topological insulator with an undamped surface electric current are considered. Dispersion relations are given for guided waves that are surface waves polarized differently on either side of the media interface and create a coupling state due to the magnetoelectric effect.
Surface Waves on the Interface Between Hyperbolic Material and Topological Insulator. 1
2017
Ekaterina I. Lyashko, Andrei I. Maimistov, 3 and Ildar R. Gabitov 5 Department of General and Applied Physics, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, 141700 Russia E-mails: ostroukhova.ei@gmail.com Department of Solid State Physics and Nanostructures, National Nuclear Research University, Moscow Engineering Physics Institute, Moscow, 115409 Russia E-mails: aimaimistov@gmail.com Department of General Physics, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, 141700 Russia Department of Mathematics, University of Arizona, Tucson, Arizona, 85721, USA Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Moscow 143026 Russia E-mails: gabitov@math.arizona.edu (Dated: June 20, 2017)
Optics and Spectroscopy, 2019
The surface waves that propagate along the interface of a dielectric with nonlinear susceptibility of the third order and topological insulator have been considered. The optical nonlinearity of the dielectric ensures the existence of a surface wave. The density of the spin angular momentum of a surface wave has been determined for dielectrics with positive or negative linear permittivity. It has been shown that the spin angular momentum vector has a projection on the normal to the interface, which is different from the usual surface polaritons or plasmon polaritons. The discrete nature of the topological number manifests itself in the discreteness of the values of the normal and tangential components of the spin angular momentum density. The increase in the intensity of the electric field of the wave at the interface of the media changes the value of the spin angular momentum and can lead to its disappearance.
Junction between surfaces of two topological insulators
Physical Review B, 2012
We study the properties of a line junction which separates the surfaces of two three-dimensional topological insulators. The velocities of the Dirac electrons on the two surfaces may be unequal and may even have opposite signs. For a time reversal invariant system, we show that the line junction is characterized by an arbitrary parameter α which determines the scattering from the junction. If the surface velocities have the same sign, we show that there can be edge states which propagate along the line junction with a velocity and orientation of the spin which depend on α and the ratio of the velocities. Next, we study what happens if the two surfaces are at an angle φ with respect to each other. We study the scattering and differential conductance through the line junction as functions of φ and α. We also find that there are edge states which propagate along the line junction with a velocity and spin orientation which depend on φ. Finally, if the surface velocities have opposite signs, we find that the electrons must transmit into the two-dimensional interface separating the two topological insulators.
Dielectric screening of surface states in a topological insulator.
Phys. Rev. B 89, 035419 (2014)
Hexagonal warping provides an anisotropy to the dispersion curves of the helical Dirac fermions that exist at the surface of a topological insulator. A sub-dominant quadratic in momentum term leads to an asymmetry between conduction and valence band. A gap can also be opened through magnetic doping. We show how these various modifications to the Dirac spectrum change the polarization function of the surface states and employ our results to discuss their effect on the plasmons. In the long wavelength limit, the plasmon dispersion retains its square root dependence on its momentum, boldsymbolq\boldsymbol{q}boldsymbolq, but its slope is modified and it can acquire a weak dependence on the direction of boldsymbolq\boldsymbol{q}boldsymbolq. Further, we find the existence of several plasmon branches, one which is damped for all values of boldsymbolq\boldsymbol{q}boldsymbolq, and extract the plasmon scattering rate for a representative case.
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 mag-netoelectric polarizability properties of the medium. To this end we employ the Green's function method to find the fields resulting form 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 = 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.