# Photocurrents in gyrotropic Weyl semimetals

## TL;DR

This paper theoretically investigates photocurrents in gyrotropic Weyl semimetals, revealing conditions for circular and magneto-induced photocurrents, and analyzing their microscopic mechanisms under magnetic fields.

## Contribution

It identifies the specific symmetry conditions and Hamiltonian terms necessary for photocurrents in gyrotropic Weyl semimetals and explores their microscopic origins.

## Key findings

- Circular photocurrent appears only with certain Hamiltonian terms.
- A polarization-independent magneto-induced photocurrent is predicted.
- Photocurrent in C2v crystals arises from optical transitions between magnetic subbands.

## Abstract

We present results of a theoretical study of photocurrents in the Weyl semimetals belonging to the gyrotropic symmetry classes. We show that, in weakly gyrotropic symmetry classes C$_{nv}$ ($n = 3,4,6$), the circular photocurrent transverse to the incidence direction appears only with account, in the electron effective Hamiltonian, for both linear and quadratic or cubic in quasi-momentum spin-dependent terms as well as a spin-independent term resulting in the tilt of the cone dispersion. A polarization-independent magneto-induced photocurrent is predicted which is also allowed in gyrotropic systems only. For crystals of the C$_{2v}$ symmetry, we consider a microscopic mechanism of the photocurrent in a quantized magnetic field which is generated under direct optical transitions between the ground and the first excited magnetic subbands. It is shown that this current becomes nonzero with allowance for anisotropic tilt of the dispersion cones.