Chiral anomaly and optical absorption in Weyl semimetals

TL;DR

This paper proposes an optical absorption experiment to detect the chiral anomaly in Weyl semimetals, showing that an applied  field induces observable features in optical conductivity related to charge transfer between chiral points.

Contribution

It introduces a novel optical method to observe the chiral anomaly in Weyl semimetals using the Kubo formula and analyzes the effects of scattering and temperature on the signal.

Findings

Step-like features in optical conductivity under  field

Observable at low temperatures in pure samples

Method to map scattering rate via  field application

Abstract

Weyl semimetals are a three-dimensional topological phase of matter with isolated band touchings in the Brillouin Zone. These points have an associated chirality, and many of the proposals to detect the Weyl semimetal state rely on the chiral anomaly. A consequence of the chiral anomaly is that under the application of an $\vec{E}\cdot\vec{B}$ field, charge is transferred between points of opposite chirality. In this paper we propose an optical absorption experiment that provides evidence for the chiral anomaly. We use the Kubo formula, and find that an applied $\vec{E}\cdot\vec{B}$ induces the formation of step-like features at finite frequency in the interband optical conductivity. We study the effect of scattering, and finite temperatures on this feature and find that it should be observable at low temperatures in pure samples. Finally we discuss how the application of an $\vec{E}\cdot\vec{B}$ field can be used to map out the frequency dependence of the scattering rate.