Chiral anomaly and transport in Weyl metals

TL;DR

This paper reviews transport phenomena in Weyl metals, emphasizing the role of chiral anomaly in phenomena like the anomalous Hall effect and chiral magnetic effect, and predicts a distinctive negative magnetoresistance as a key experimental signature.

Contribution

It provides a microscopic theory linking chiral anomaly to transport properties in Weyl metals, highlighting the intrinsic nature of the anomalous Hall effect and predicting a unique negative magnetoresistance.

Findings

AHE in Weyl metals is purely intrinsic and determined by Weyl node positions.

Chiral magnetic effect leads to magnetic-field-induced coupling of charge densities.

Negative quadratic magnetoresistance is a hallmark of Weyl metals.

Abstract

We present an overview of our recent work on transport phenomena in Weyl metals, which may be connected to their nontrivial topological properties, particularly to chiral anomaly. We argue that there are two basic phenomena, which are related to chiral anomaly in Weyl metals: Anomalous Hall Effect (AHE) and Chiral Magnetic Effect (CME). While AHE is in principle present in any ferromagnetic metal, we demonstrate that a magnetic Weyl metal is distinguished from an ordinary ferromagnetic metal by the absence of the extrinsic and the Fermi surface part of the intrinsic contributions to the AHE, as long as the Fermi energy is sufficiently close to the Weyl nodes. The AHE in a Weyl metal is thus shown to be a purely intrinsic, universal property, fully determined by the location of the Weyl nodes in the first Brillouin zone. In other words, a ferromagnetic Weyl metal may be thought of as the only example of a ferromagnetic metal with a purely intrinsic AHE. We further develop a fully microscopic theory of diffusive magnetotransport in Weyl metals. We derive coupled diffusion equations for the total and axial (i.e. node-antisymmetric) charge densities and show that chiral anomaly manifests as a magnetic-field-induced coupling between them. We demonstrate that an experimentally-observable consequence of CME in magnetotransport in Weyl metals is a quadratic negative magnetoresistance, which will dominate all other contributions to magnetoresistance under certain conditions and may be regarded as a smoking-gun transport characteristic, unique to Weyl metals.