Disentangling thermal and non-thermal excited states in a charge-transfer insulator by time-and-frequency resolved pump-probe spectroscopy

TL;DR

This study uses time-and-frequency resolved pump-probe spectroscopy to distinguish between thermal and non-thermal excited states in a charge-transfer insulator, revealing a metastable non-thermal state induced by impulsive excitation.

Contribution

It demonstrates the ability to disentangle thermal and non-thermal states in a charge-transfer insulator using advanced spectroscopic techniques, highlighting the creation of a metastable non-thermal state.

Findings

Broadening of charge-transfer edge on sub-ps timescale

Modification not due to local temperature increase

Evidence of a metastable non-thermal state

Abstract

Time-and-frequency resolved pump-probe optical spectroscopy is used to investigate the effect of the impulsive injection of delocalized excitations through a charge-transfer process in insulating CuGeO3. A large broadening of the charge-transfer edge is observed on the sub-ps timescale. The modification of this spectral feature can not be attributed to the local increase of the effective temperature, as a consequence of the energy absorbed by the pump pulse. The measured modifications of the optical properties of the system are consistent with the creation of a non-thermal state, metastable on the ps timescale, after the pump-induced impulsive modification of the electron interactions.