Magnetic dynamics with Weyl fermions

TL;DR

This paper develops a thermodynamic framework to analyze charge and valley transport in magnetic Weyl semimetals, revealing how valley degrees of freedom mediate coupling between charge and magnetic dynamics, including dissipation and instabilities.

Contribution

It introduces a systematic analysis of dissipative couplings and collective dissipation in magnetic Weyl semimetals, extending previous topological studies with new insights into valley-mediated interactions.

Findings

Valley degrees of freedom mediate charge-magnetic coupling.

Identification of valley-mediated current-driven magnetic instabilities.

Extension of theory to antiferromagnetic Weyl semimetals.

Abstract

Transport of charge and valley degrees of freedom coupled to order-parameter dynamics in magnetic Weyl semimetals is studied in the framework of nonequilibrium thermodynamics. In addition to the established valley-related transport anomalies that are rooted in band-structure topology, we construct dissipative couplings between the three dynamic constituents of the system driven out of equilibrium by electromagnetic perturbations. We show how the valley degree of freedom mediates an effective coupling between the charge and magnetic sectors of the system, through a combination of the chiral anomaly, on the electric side, and the Onsager-paired valley torque and pumping, on the magnetic side. This work compliments previous studies of magnetic Weyl semimetals by a more systematic analysis of collective dissipation. We discuss several concrete examples of the valley-mediated current-driven magnetic instabilities and charge pumping, and extend the theory to the antiferromagnetic case.