Kerr and Faraday rotations in a Weyl semimetal in a strong magnetic field

One striking property of the Landau level spectrum of a Weyl semimetal (WSM) is the existence of a chiral Landau level (CLL) in which the electrons propagate unidirectionnaly along the magnetic field. This linearly dispersive level influences the optical properties of WSMs. For example, it was shown that a complete optical valley polarization is achievable in a time-reversal symmetric WSM placed in a strong magnetic field [1]. This effect originates from interband transitions involving the CLL and requires a tilt of the Weyl cones in the hamiltonian. In this talk, we show how the presence of the CLL changes the behavior of the Kerr and Faraday rotations of an electromagnetic wave incident on a WSM in a strong magnetic field with respect to a non-topological metal. To calculate the optical conductivity tensor σ_αβ(ω), we use the minimal model of a WSM developed in Ref. [1] with four tilted Weyl nodes related by mirror and time-reversal symmetry. We present the dependency of the Kerr and Faraday angles on the tilt angle of the cones, the position of the Fermi level, the thickness of the WSM and the magnetic field intensity in both the resonant and non-resonant frequency regimes.

[1] S. Bertrand, Jean-Michel Parent, R. Côté, and I. Garate, Phys. Rev. B 100, 075107 (2019).