Coulomb Drag in Altermagnets

TL;DR

This paper proposes using Coulomb drag measurements to detect and characterize altermagnetism, revealing unique angle-dependent Hall drag effects that distinguish altermagnets from other magnetic systems.

Contribution

It introduces a novel method employing Coulomb drag to probe the anisotropic spin-split bands in altermagnets, enabling experimental identification of altermagnetism without spin-orbit coupling.

Findings

Coulomb drag effects are highly sensitive to spin-split Fermi surface orientation.

Transverse currents and Hall drag effects can occur without spin-orbit coupling.

Drag effects exhibit unique angle dependence serving as signatures of altermagnetism.

Abstract

An altermagnet is a newly discovered antiferromagnet, characterized by unique anisotropic spin-split energy bands. It has attracted tremendous interest, because of its promising potential in information storage and processing. However, measuring the distinctive spin-split energy bands arising from altermagnetism remains a challenge. Here, we propose to employ the Coulomb drag to probe altermagnetism. In the Coulomb drag, an electric current in an active layer of electron gases can induce currents in a close but well-isolated passive layer, due to interlayer Coulomb interactions. We find that the Coulomb drag effects in altermagnets are highly sensitive to the orientation of the spin-split Fermi surfaces. As a result, transverse currents can be dragged in the passive layer, leading to Hall drag effects even in absence of spin-orbit coupling, a feature quite different from all previous systems. More importantly, all the drag effects of altermagnets have unique angle dependence, which can be measured in a multi-terminal setup to serve as signatures for altermagnetism. This proposal will inspire increasing explorations on emergent magnetism.