Kramers degeneracy in a magnetic field and Zeeman spin-orbit coupling in antiferromagnetic conductors

TL;DR

This paper explores how a hidden symmetry in antiferromagnetic conductors protects electron degeneracy against magnetic fields, leading to a Zeeman spin-orbit coupling that varies with momentum and affects a range of materials.

Contribution

It reveals a hidden anti-unitary symmetry that preserves Kramers degeneracy in antiferromagnets, introducing a momentum-dependent Zeeman spin-orbit coupling.

Findings

Kramers degeneracy is protected at specific momenta by hidden symmetry.

The Zeeman term acts as a spin-orbit coupling with momentum dependence.

Applicable to various materials including chromium, cuprates, and heavy fermion conductors.

Abstract

In this article, I study magnetic response of electron wavefunctions in a commensurate collinear antiferromagnet. I show that, at a special set of momenta, hidden anti-unitary symmetry protects Kramers degeneracy of Bloch eigenstates against a magnetic field, pointing transversely to staggered magnetization. Hence a substantial momentum dependence of the transverse g-factor in the Zeeman term, turning the latter into a spin-orbit coupling, that may be present in materials from chromium to borocarbides, cuprates, pnictides, as well as organic and heavy fermion conductors.