Time-resolved optical observation of spin-wave dynamics

TL;DR

This study uses time-resolved nonlinear optical spectroscopy to observe and model the dynamics of antiferromagnetic spin-waves in Cr2O3, revealing how optical excitation affects their band structure and thermalization.

Contribution

It introduces a novel experimental approach to directly observe spin-wave dynamics and proposes a model explaining the observed optical nonlinearities and thermalization processes.

Findings

Time-dependent pump-probe line shape observed

Optical nonlinearity dominated by interactions with long-wavelength spin-waves

Spin-wave thermalization explains the dynamics

Abstract

We have created a nonequilibrium population of antiferromagnetic spin-waves in Cr2O3, and characterized its dynamics, using frequency- and time-resolved nonlinear optical spectroscopy of the exciton-magnon transition. We observe a time-dependent pump-probe line shape, which results from excitation induced renormalization of the spin-wave band structure. We present a model that reproduces the basic characteristics of the data, in which we postulate the optical nonlinearity to be dominated by interactions with long-wavelength spin-waves, and the dynamics to be due to spin-wave thermalization.