Quantized electrochemical transport in Weyl semimetals

TL;DR

This paper demonstrates that Weyl semimetals exhibit a nearly quantized topological electric current under external electric fields and chemical potential gradients, linked to their topological charge and chiral anomaly.

Contribution

It provides analytic expressions for nonlinear conductivity in Weyl semimetals and reveals conditions for fully quantized electrochemical responses related to topological properties.

Findings

Nearly quantized nonlinear conductivity for small tilting.

Full quantization of electrochemical response when Fermi levels are near Weyl nodes.

Electrochemical chiral current derived from an axion-like electromagnetic action.

Abstract

We show that under the effect of an external electric field and a gradient of chemical potential, a topological electric current can be induced in Weyl semimetals without inversion and mirror symmetries. We derive analytic expressions for the nonlinear conductivity tensor and show that it is nearly quantized for small tilting when the Fermi levels are close to the Weyl nodes. When the van Hove point is much larger than the largest Fermi level, the band structure is described by two linearly dispersing Weyl fermions with opposite chirality. In this case, the electrochemical response is fully quantized in terms of fundamental constants and the scattering time, and it can be used to measure directly the topological charge of Weyl points. We show that the electrochemical chiral current may be derived from an electromagnetic action similar to axion electrodynamics, where the position-dependent chiral Fermi level plays the role of the axion field. This posits our results as a direct consequence of the chiral anomaly.