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Electron magnetism of antiferromagnetic conductors

par Revaz Ramazashvili - 9 mars 2017

This is the subject of my very first papers, written in Russia as a masters student of Serguei Brazovskii, soon after the discovery of high-Tc superconductivity :

S. Brazovskii, I. Luk’yanchuk, and RR, JETP Letters 49, 644 (1989)

The parent compounds of the cuprates are antiferromagnetic Mott insulators, and thus a doped antiferromagnetic insulator has been at the center of much theoretical work on the subject ever since the discovery of high-Tc.

Among other things, I had stumbled upon the possibility to excite electron spin resonance transitions in a low carrier-density antiferromagnet by an electric rather than magnetic field :

RR, Sov. Phys. JETP 73, 505 (1991)

Curiously enough, I returned to this topic some twenty years later, and was able to develop the symmetry underpinnings of the Zeeman spin-orbit coupling in antiferromagnetic conductors : It turns out that, in a transverse magnetic field, the symmetry of a Néel antiferromagnet remains high enough to protect double degeneracy of Bloch eigenstates at certain special momenta in the Brillouin zone. As a result, the transverse component of the electron g-tensor vanishes at such momenta, and thus acquires a substantial momentum dependence, which turns the textbook Zeeman term into a veritable spin-orbit coupling :

RR, Phys. Rev. Lett. 101, 137202 (2008)

RR, Phys. Rev. B 79, 184432 (2009)

RR, Phys. Rev. B 80, 054405 (2009)

RR, Phys. Rev. Lett. 105, 216404 (2010)

More recently, I returned to the subject yet again, having contributed an invited review article to the Topical Issue on Spin-Orbit Coupled Materials of the Journal of Physics and Chemistry of Solids. In this article, I attempted to give a pedagogical overview of the Zeeman spin-orbit coupling — and to contrast it with some other known occurrences of spin-orbit terms :

RR, JPCS 128, 65 (2019).

Most recently, early 2021 brought what appears to be the first published experimental evidence for Zeeman spin–orbit coupling in antiferromagnetic conductors. The experiments, carried out on two different layered antiferromagnetic materials, were inspired and led by Mark Kartsovnik of Walther-Meißner-Institut in Munich.