Non-universality of the adiabatic chiral magnetic effect in a clean Weyl semimetal slab

TL;DR

This paper investigates the adiabatic chiral magnetic effect in a ballistic Weyl semimetal slab, revealing that boundary Fermi arc states can dominate the effect under certain conditions, challenging the notion of topological invariance.

Contribution

It demonstrates that the Fermi arc contribution to the CME is not generally topologically invariant and can be computed from the low-energy Weyl Hamiltonian for specific boundary conditions.

Findings

Fermi arc states can dominate the CME in certain boundary conditions.

The Fermi arc contribution is not topologically invariant.

The contribution can be calculated from the Weyl Hamiltonian and scattering phase.

Abstract

The adiabatic chiral magnetic effect (CME) is a phenomenon by which a slowly oscillating magnetic field applied to a conducting medium induces an electric current in the instantaneous direction of the field. Here we theoretically investigate the effect in a ballistic Weyl semimetal sample having the geometry of a slab. We discuss why in a general situation the bulk and the boundary contributions towards the CME are comparable. We show, however, that under certain conditions the adiabatic CME is dominated by the Fermi arc states at the boundary. We find that despite the topologically protected nature of the Fermi arcs, their contribution to the CME is neither related to any topological invariant nor can generally be calculated within the bulk low-energy effective theory framework. For certain types of boundary, however, the Fermi arcs contribution to the CME can be found from the effective low energy Weyl Hamiltonian and the scattering phase characterising the collision of a Weyl excitation with the boundary.