A Microscopic Model of Non-Reciprocal Optical Effects in Cr_2 O_3

TL;DR

This paper develops a microscopic model explaining how light directly couples to antiferromagnetic order in Cr_2 O_3, revealing the origin of non-reciprocal optical effects through spin-orbit interaction and symmetry considerations.

Contribution

It introduces a novel microscopic framework that elucidates the direct coupling mechanism between light and antiferromagnetic order in Cr_2 O_3.

Findings

Light couples directly to the antiferromagnetic order parameter.

Spin-orbit interaction mediates the coupling.

Inversion symmetry breaking is crucial for non-reciprocal effects.

Abstract

This manuscript deals with the question "How does light couple to an antiferromagnetic order parameter"? For that we develop a microscopic model that explains the non-reciprocal optical effects in centrosymmetric Cr_2 O_3. It is shown that light can couple {\em directly} to the antiferromagnetic order parameter. This coupling is mediated by the spin-orbit interaction and involves an interplay between the breaking of inversion symmetry due to the antiferromagnetic order parameter and the trigonal field contribution to the ligand field at the Cr^{3+} ion.