Femtosecond dynamics of magnetic excitations from resonant inelastic x-ray scattering in CaCu2O3

TL;DR

This paper demonstrates that femtosecond magnetic excitation dynamics in CaCu2O3 can be probed using resonant inelastic x-ray scattering, revealing different timescales for single and double spin-flip processes.

Contribution

It shows how RIXS can be used to access the time-domain dynamics of magnetic excitations and differentiate between them based on their temporal behavior.

Findings

Double spin flips require finite time to generate and are sensitive to core-hole lifetime.

Single spin flips are largely independent of core-hole lifetime.

RIXS can distinguish excitation types by their time dependence.

Abstract

Taking spinon excitations in the quantum antiferromagnet CaCu2O3 as an example, we demonstrate that femtosecond dynamics of magnetic excitations can be probed by direct resonant inelastic x-ray scattering (RIXS). To this end, we isolate the contributions of single and double spin-flip excitations in experimental RIXS spectra, identify the physical mechanisms that cause them and determine their respective timescales. By comparing theory and experiment, we find that double spin flips need a finite amount of time to be generated, rendering them sensitive to the core-hole lifetime, whereas single spin flips are to a very good approximation independent of it. This shows that RIXS can grant access to time-domain dynamics of excitations and illustrates how RIXS experiments can distinguish between excitations in correlated electron systems based on their different time dependence.