Consistent Chiral Kinetic Theory in Weyl Materials: Chiral Magnetic Plasmons

TL;DR

This paper develops a consistent chiral kinetic theory for Weyl materials that incorporates Chern-Simons contributions, revealing novel chiral plasmon modes and their dependence on magnetic fields, which could enable parameter extraction from experiments.

Contribution

It introduces a corrected kinetic theory including Chern-Simons terms, ensuring charge conservation and analyzing collective plasma modes in Weyl materials under magnetic fields.

Findings

Identification of chiral plasmons with coupled electric and chiral current oscillations

Discovery of plasma frequency splitting in transverse modes under magnetic fields

Proposal of a method to extract the chiral shift parameter from plasma frequency measurements

Abstract

We argue that the correct definition of the electric current in the chiral kinetic theory for Weyl materials should include the Chern-Simons contribution that makes the theory consistent with the local conservation of the electric charge in electromagnetic and strain-induced pseudoelectromagnetic fields. By making use of such a kinetic theory, we study the plasma frequencies of collective modes in Weyl materials in constant magnetic and pseudomagnetic fields, taking into account the effects of dynamical electromagnetism. We show that the collective modes are chiral plasmons. While the plasma frequency of the longitudinal collective mode coincides with the Langmuir one, this mode is unusual because it is characterized not only by oscillations of the electric current density, but also by oscillations of the chiral current density. The latter are triggered by a dynamical version of the chiral electric separation effect. We also find that the plasma frequencies of the transverse modes split up in a magnetic field. This finding suggests an efficient means of extracting the chiral shift parameter from the measurement of the plasma frequencies in Weyl materials.