Ultrafast magnetic dynamics in insulating YBa$_2$Cu$_3$O$_{6+x}$ revealed by time resolved two-magnon Raman Scattering

TL;DR

This study introduces a novel time-resolved two-magnon Raman scattering technique to investigate ultrafast magnetic dynamics in the antiferromagnetic insulator YBa₂Cu₃O₆₊ₓ, revealing rapid demagnetization and slow relaxation processes.

Contribution

It demonstrates the application of time-resolved two-magnon Raman scattering as a new method to probe magnetic correlations in antiferromagnets in real time.

Findings

Rapid demagnetization within 90 fs after photoexcitation.

Slower relaxation back to equilibrium characterized by distinct timescales.

Magnetic sector quickly reaches a prethermal state while charge sector relaxes slowly.

Abstract

Measurement and control of magnetic order and correlations in real time is a rapidly developing scientific area relevant for magnetic memory and spintronics [1,15]. In these experiments an ultra-short laser pulse (pump) is first absorbed by excitations carrying electric dipole moment. These then give their energy to the magnetic subsystem monitored by a time-resolved probe. A lot of progress has been made in investigations of ferromagnets but antiferromagnets are more challenging. Here we introduce time-resolved two-magnon Raman scattering as a novel real time probe of magnetic correlations especially well-suited for antiferromagnets. Its application to the antiferromagnetic charge transfer insulator YBa$_2$Cu$_3$O$_{6+x}$ revealed rapid demagnetization within 90fs of photoexcitation. The relaxation back to thermal equilibrium is characterized by much slower timescales. We interpret these results in terms of slow relaxation of the charge sector and rapid equilibration of the magnetic sector to a prethermal state characterized by parameters that change slowly as the charge sector relaxes.