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

Time- and frequency-resolved pump-probe optical spectroscopy is used to investigate the effects 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 time scale. The modification of this spectral feature cannot be attributed to the local increase in 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 nonthermal state, metastable on the picosecond time scale, after the pump-induced impulsive modification of the electron interactions.

strongly correlated systems ; nonequilibrium dynamics ; CuGeO3 ; pump-probe ; femtosecond

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