Chiral filtration and Faraday rotation in multi-Weyl semimetals

In Weyl semimetals with broken inversion and time-reversal symmetries, the Maxwell equations are modified by the presence of the axion terms $\mathbf{b} $ and $b_{0}$ where, in the simplest case of a two-node Weyl semimetal, $% 2\hslash \mathbf{b}$ is the vector that connects two Weyl nodes in momentum space and $2\hslash b_{0}$ is the separation in energy of the two Dirac points of these nodes. These axion terms modify the behavior of electromagnetic waves inside a Weyl semimetal leading to a number of unique optical properties such as non-reciprocal propagation, circular and linear dichroism, birefringence and Faraday and Kerr rotations in the absence of a magnetic field. These effects can be used to design optical devices that act as broadband chiral filters, circular polarizers or tunable optical isolators. In this paper, we study in detail how the Faraday and Kerr rotations as well as the transmission and reflection of light incident on a slab of Weyl semimetal can be controlled by varying the different parameters characterizing the Weyl semimetal such as the axion terms, the Fermi level and Fermi velocity, the background dielectric constant, the scattering time for intraband scattering, the width of the semimetal and the dielectric constant of the dielectrics on each side of the semimetal slab. We extend our analysis to Weyl nodes with Chern number $n=1,2,3$.