# Absorption of circular polarized light in tilted Type-I and II Weyl semimetals

## TL;DR

This paper investigates how circularly polarized light interacts with tilted Weyl semimetals, revealing distinct optical responses depending on tilt type and polarization, with implications for understanding their electronic properties.

## Contribution

It provides a detailed analysis of the optical response of tilted Weyl semimetals to circularly polarized light, including type-I and II, highlighting the effects of tilt and polarization reversal.

## Key findings

- Distinct optical responses for RHP and LHP in type-I within specific photon energy ranges.
- In type-II Weyl semimetals, the response range extends without an upper bound.
- Reversing tilt direction swaps the RHP and LHP responses.

## Abstract

We calculate the A.C. optical response to circularly polarized light of a Weyl semimetal (WSM) with varying amounts of tilt of the Dirac cones. Both type-I and II (overtilted) WSM are considered in a continuum model with broken time reversal (TR) symmetry. The Weyl nodes appear in pairs of equal energies but of opposite momentum and chirality. For type-I the response of a particular node to right (RHP) and left (LHP) hand polarized light are distinct only in a limited range of photon energy $\Omega$, $\frac{2}{1+C_{2}/v}<\frac{\Omega}{\mu}<\frac{2}{1-C_{2}/v}$ with $\mu$ the chemical potential and $C_{2}$ the tilt associated with the positive chirality node assuming the two nodes are oppositely tilted. For the over tilted case (type-II) the same lower bound applies but there is no upper bound. If the tilt is reversed the RHP and LHP response are also reversed. We present corresponding results for the Hall angle.