Optical evidence of the chiral magnetic anomaly in Weyl semimetal TaAs

TL;DR

This study provides optical evidence of the chiral magnetic anomaly in Weyl semimetal TaAs, demonstrating chiral pumping, free carrier spectral weight enhancement, and field-dependent Fermi velocity, confirming key theoretical predictions.

Contribution

First direct optical measurement of chiral pumping and spectral weight changes in TaAs, revealing field-dependent Fermi velocity and supporting the chiral magnetic effect in Weyl semimetals.

Findings

Observation of chiral pumping at THz frequencies

Direct measurement of free carrier spectral weight enhancement

Evidence of field-dependent Fermi velocity in the quantum limit

Abstract

Chiral pumping from optical electric fields oscillating at THz frequencies is observed in the Weyl material TaAs with electric and magnetic fields aligned along both the a- and c-axes. Free carrier spectral weight enhancement is measured directly for the first time, confirming theoretical expectations of chiral pumping. A departure from linear field-dependence of the Drude weight is observed at the highest fields in the quantum limit, providing direct evidence of field-dependent Fermi velocity of the chiral Landau level. Implications for the chiral magnetic effect in Weyl semimetals from the optical f-sum rule are discussed.