# Optical Signatures of the Chiral Anomaly in Mirror-Symmetric Weyl Semimetals

## TL;DR

This paper proposes a new optical method to detect the chiral anomaly in mirror-symmetric Weyl semimetals by observing IR reflectivity peaks influenced by magnetic fields, expanding detection possibilities beyond non-mirror-symmetric crystals.

## Contribution

It demonstrates that mirror-symmetric Weyl semimetals can exhibit observable chiral anomaly signatures through optical phonon responses under magnetic fields, even with scalar phonon modes.

## Key findings

- IR reflectivity peak develops with magnetic field in mirror-symmetric Weyl semimetals.
- Zeeman interaction at 10T induces detectable signatures of the chiral anomaly.
- Signatures depend on the dot product of IR electric field and magnetic field.

## Abstract

The chiral anomaly is a phenomenon characteristic of Weyl fermions, which has condensed matter realizations in Weyl semimetals. Efforts to observe smoking gun signatures of the chiral anomaly in Weyl semimetals have mostly focused on a negative longitudinal magnetoresistance in electronic transport. Unfortunately, disentangling the chiral anomaly contribution in transport or optical measurements has proven non-trivial. Recent works have proposed an alternative approach of probing pseudoscalar phonon dynamics for signatures of the chiral anomaly in non-mirror-symmetric crystals. Here, we show that such phonon signatures can be extended to scalar phonon modes and mirror-symmetric crystals, broadening the pool of candidate materials. We show that the presence of the background magnetic field can break mirror symmetry strongly enough to yield observable signatures of the chiral anomaly even in mirror-symmetric materials. Specifically for mirror-symmetric Weyl semimetals such as TaAs and NbAs, including the Zeeman interaction at $B \approx 10$T, we predict an IR reflectivity peak will develop with an $\mathbf{E}_\text{IR}\cdot\mathbf{B}$ dependence.