Probing charge pumping and relaxation of the chiral anomaly in a Dirac semimetal

Bing Cheng; Timo Schumann; Susanne Stemmer; N P Armitage

doi:10.1126/sciadv.abg0914

Probing charge pumping and relaxation of the chiral anomaly in a Dirac semimetal

Sci Adv. 2021 Apr 16;7(16):eabg0914. doi: 10.1126/sciadv.abg0914. Print 2021 Apr.

Authors

Bing Cheng¹, Timo Schumann², Susanne Stemmer², N P Armitage³

Affiliations

¹ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
² Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
³ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA. [email protected].

Abstract

The linear band crossings of 3D Dirac and Weyl semimetals are characterized by a charge chirality, the parallel or antiparallel locking of electron spin to its momentum. These materials are believed to exhibit an E · B chiral magnetic effect that is associated with the near conservation of chiral charge. Here, we use magneto-terahertz spectroscopy to study epitaxial Cd₃As₂ films and extract their conductivities σ(ω) as a function of E · B. As field is applied, we observe a markedly sharp Drude response that rises out of the broader background. Its appearance is a definitive signature of a new transport channel and consistent with the chiral response, with its spectral weight a measure of the net chiral charge and width a measure of the scattering rate between chiral species. The field independence of the chiral relaxation establishes that it is set by the approximate conservation of the isospin that labels the crystalline point-group representations.

Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).