Collective excitations in Weyl semimetals in the hydrodynamic regime

TL;DR

This paper investigates the spectrum of collective excitations in Weyl semimetals within a hydrodynamic framework that incorporates chiral anomaly effects and node separations, predicting novel wave modes influenced by these topological features.

Contribution

It introduces a comprehensive hydrodynamic model including chiral anomaly and node separation effects, revealing new collective excitation modes in Weyl semimetals.

Findings

Certain collective modes are affected by the chiral shift even without magnetic fields.

Predicted longitudinal and transverse anomalous Hall waves with linear dispersion.

Oscillations involve electric charge density and electromagnetic fields linked by the anomalous Hall effect.

Abstract

The spectrum of collective excitations in Weyl materials is studied by using consistent hydrodynamics. The corresponding framework includes the vortical and chiral anomaly effects, as well as the dependence on the separations between the Weyl nodes in energy $b_0$ and momentum $\mathbf{b}$. The latter are introduced via the Chern-Simons contributions to the electric current and charge densities in Maxwell's equations. It is found that, even in the absence of a background magnetic field, certain collective excitations (e.g. the helicon-like modes and the anomalous Hall waves) are strongly affected by the chiral shift $\mathbf{b}$. In a background magnetic field, the existence of the distinctive longitudinal and transverse anomalous Hall waves with a linear dispersion relation is predicted. They originate from the oscillations of the electric charge density and electromagnetic fields, in which different components of the fields are connected via the anomalous Hall effect in Weyl semimetals.