Theory of electromagnetic wave propagation in ferromagnetic Rashba conductor
Abstract
We present a comprehensive study of various electromagnetic wave propagation phenomena in a ferromagnetic bulk Rashba conductor from the perspective of quantum mechanical transport. In this system, both the space inversion and time reversal symmetries are broken, as characterized by the Rashba field α and magnetization M, respectively. First, we present a general phenomenological analysis of electromagnetic wave propagation in media with broken space inversion and time reversal symmetries based on the dielectric tensor. The dependence of the dielectric tensor on the wave vector q and M is retained to first order. Then, we calculate the microscopic electromagnetic response of the current and spin of conduction electrons subjected to α and M, based on linear response theory and the Green's function method; the results are used to study the system optical properties. First, it is found that a large α enhances the anisotropic properties of the system and enlarges the frequency range in which the electromagnetic waves have hyperbolic dispersion surfaces and exhibit unusual propagations known as negative refraction and backward waves. Second, we consider the electromagnetic crosscorrelation effects (direct and inverse Edelstein effects) on the wave propagation. These effects stem from the lack of space inversion symmetry and yield qlinear offdiagonal components in the dielectric tensor. This induces a Rashbainduced birefringence, in which the polarization vector rotates around the vector (α ×q ) . In the presence of M, which breaks time reversal symmetry, there arises an anomalous Hall effect and the dielectric tensor acquires offdiagonal components linear in M. For α ∥M , these components yield the Faraday effect for the Faraday configuration q ∥M and the CottonMouton effect for the Voigt configuration ( q ⊥M ). When α and M are noncollinear, M and qinduced optical phenomena are possible, which include nonreciprocal directional dichroism in the Voigt configuration. In these nonreciprocal optical phenomena, a "toroidal moment," α ×M , and a "quadrupole moment," α_{i}M_{j}+M_{i}α_{j} , play central roles. These phenomena are strongly enhanced at the spinsplit transition edge in the electron band.
 Publication:

Journal of Applied Physics
 Pub Date:
 February 2018
 DOI:
 10.1063/1.5011130
 arXiv:
 arXiv:1709.03689
 Bibcode:
 2018JAP...123f3902S
 Keywords:

 Condensed Matter  Mesoscale and Nanoscale Physics
 EPrint:
 45 pages, 20 figures