Signature of antiferromagnetic long-range order in the optical spectrum of strongly correlated electron systems

TL;DR

This paper demonstrates how optical spectroscopy can detect antiferromagnetic long-range order in strongly correlated electron systems, revealing spectral weight changes and spin-polaron peaks associated with magnetic ordering.

Contribution

The study introduces a method using dynamical mean-field theory to identify antiferromagnetic order via optical spectral features, linking theory with experimental observations.

Findings

Enhanced spectral weight above the optical gap in antiferromagnetic phase

Emergence of spin-polaron peaks in optical spectrum

Observation consistent with experimental data in LaSrMnO_4

Abstract

We show how the onset of a non-Slater antiferromagnetic ordering in a correlated material can be detected by optical spectroscopy. Using dynamical mean-field theory we identify two distinctive features: The antiferromagnetic ordering is associated with an enhanced spectral weight above the optical gap, and well separated spin-polaron peaks emerge in the optical spectrum. Both features are indeed observed in LaSrMnO_4 [G\"ossling et al., Phys. Rev. B 77, 035109 (2008)]