Dynamical density and spin response of Fermi arcs and their consequences for Weyl semimetals

TL;DR

This paper analytically derives the density-spin response tensor for Fermi-arc surface states in Weyl semimetals, revealing a magnetoelectric effect and analyzing surface plasmon dispersion, advancing understanding of their electromagnetic properties.

Contribution

It provides the first analytical expressions for the density-spin response tensor of Weyl semimetal surface states, including effects of electron interactions and surface plasmons.

Findings

Discovery of a magnetoelectric effect caused by Fermi arcs

Analytical expressions for the density-spin response tensor

Analysis of surface plasmon dispersion in Weyl semimetals

Abstract

Weyl semimetals exhibit exotic Fermi-arc surface states, which strongly affect their electromagnetic properties. We derive analytical expressions for all components of the composite density-spin response tensor for the surfaces states of a Weyl-semimetal model obtained by closing the band gap in a topological insulating state and introducing a time-reversal-symmetry-breaking term. Based on the results, we discuss the electromagnetic susceptibilities, the current response, and other physical effects arising from the density-spin response. We find a magnetoelectric effect caused solely by the Fermi arcs. We also discuss the effect of electron-electron interactions within the random phase approximation and investigate the dispersion of surface plasmons formed by Fermi-arc states. Our work is useful for understanding the electromagnetic and optical properties of the Fermi arcs.