Anomalous and Topological Hall Effects with Phase-Space Berry Curvatures: Electric, Thermal, and Thermoelectric Transport in Magnets

TL;DR

This paper develops a semiclassical theory for electrical and thermal Hall effects in magnetic materials with topological spin textures, incorporating phase-space Berry curvatures to distinguish between ordinary, anomalous, and topological responses.

Contribution

It introduces a unified semiclassical framework that accounts for all phase-space Berry curvatures affecting transport in magnetic textures, clarifying the roles of SOC and spin texture topology.

Findings

All conductivities can be decomposed into ordinary, anomalous, and topological contributions.

Derived relations like the Wiedemann-Franz and Mott relations hold at low temperatures.

The Hall response varies qualitatively depending on the strength of SOC relative to exchange coupling.

Abstract

We develop a theory for the electrical and thermal transverse linear response functions such as the Hall, Nernst and thermal Hall effects in magnetic materials that harbor topological spin textures like skyrmions. In addition to the ordinary transverse response that arises from the Lorentz force due to the external magnetic field, there is an anomalous and a topological response. The intrinsic anomalous response derives from the momentum space Berry curvature arising from the spin-orbit coupling (SOC) in a system with a nonzero magnetization, while the topological response arises from real space Berry curvature related to the the topological charge density of the spin texture. To take into account all these effects on an equal footing, we develop a semiclassical theory that incorporates all phase-space Berry curvatures. We show within a controlled, semiclassical approach that all conductivities -- electrical, thermoelectric, and thermal Hall -- can be written as the sum of three contributions: ordinary, anomalous and topological, when the conduction electron SOC is weaker than the exchange coupling to the spin texture. All other contributions, including those arising from mixed real-momentum space Berry curvature, are negligible in the regime where our calculations are controlled. We derive various general relations that remain valid at low temperatures including the Weidemann-Franz relation between the electrical and thermal conductivities and the Mott relation between the thermoelectric and electrical conductivities. We also discuss how an in-plane Hall response arises in three-dimensional materials with sufficiently low symmetry. Finally, the Hall response is qualitatively different when the conduction electron SOC is stronger than the exchange coupling to the spin texture, where we find that the anomalous term dominates and the topological term vanishes.