Dynamical chiral magnetic current and instability in Weyl semimetals

TL;DR

This paper investigates the dynamical chiral magnetic effect and related instabilities in Weyl semimetals, revealing how time-dependent magnetic fields induce currents and lead to electromagnetic instabilities, with implications for their electromagnetic response.

Contribution

It provides a theoretical analysis of dynamical chiral magnetic effects and instabilities in Weyl semimetals using effective field theory and chiral kinetic theory, including dissipation effects.

Findings

Dynamical magnetic fields induce electric currents independent of temperature and chemical potential.

Identifies unstable electromagnetic modes related to Weyl node separation.

Predicts anisotropic electromagnetic wave generation due to instabilities.

Abstract

Weyl semimetals realize massless relativistic fermions with two Weyl nodes separated in energy and momentum space, whose low-energy physics is described by Dirac fermions with an axial gauge constant. Here, we study their electromagnetic linear responses based on the effective field theory and on the chiral kinetic theory. Although the static chiral magnetic effect is canceled by the Chern-Simons current under the Pauli-Villars regularization, a dynamical magnetic field is found capable of driving an electric current along its direction, with the total transported charge being independent of temperature and chemical potential for a uniform field. We also incorporate dissipation in the relaxation-time approximation and study collective excitations coupled with Maxwell electromagnetic fields when Weyl node populations deviate from equilibrium. Their dispersion relations at low frequency and long wavelength are determined only by electric, chiral magnetic, and anomalous Hall conductivities, which predict unstable modes leading to anisotropic generation of electromagnetic waves oriented to the direction of Weyl node separation.