Scattering theory of the chiral magnetic effect in a Weyl semimetal: Interplay of bulk Weyl cones and surface Fermi arcs

TL;DR

This paper develops a scattering theory approach to analyze the chiral magnetic effect in Weyl semimetals, highlighting the significant and universal role of surface Fermi arcs alongside bulk Weyl cones.

Contribution

It introduces a linear response framework connecting surface and bulk contributions to the chiral magnetic effect via the scattering matrix in Weyl semimetals.

Findings

Surface Fermi arcs contribute significantly to the magnetic response.

The Fermi arc contribution to the magnetic susceptibility is universal and impurity-resistant.

Bulk and surface contributions can have opposite signs, affecting the total response.

Abstract

We formulate a linear response theory of the chiral magnetic effect in a finite Weyl semimetal, expressing the electrical current density $j$ induced by a slowly oscillating magnetic field $B$ or chiral chemical potential $\mu$ in terms of the scattering matrix of Weyl fermions at the Fermi level. Surface conduction can be neglected in the infinite-system limit for $\delta j/\delta \mu$, but not for $\delta j/\delta B$: The chirally circulating surface Fermi arcs give a comparable contribution to the bulk Weyl cones no matter how large the system is, because their smaller number is compensated by an increased flux sensitivity. The Fermi arc contribution to $\mu^{-1}\delta j/\delta B$ has the universal value $(e/h)^2$, protected by chirality against impurity scattering --- unlike the bulk contribution of opposite sign.