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

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.

Probing phase transitions under extreme conditions by ultrafast techniques: Advances at the Fermi@Elettra free-electron-laser facility

“…1 and Section 2) and absorption measurements is seen as an important tool for a detailed characterization of the onsets of the transitions. Such a set-up [17,18] has been recently developed at Fermi@Elettra and has been used for pilot experiments of the reflectivity changes near the melting threshold of the Si(100) surface, using an optical laser as a pump.…”

“…Suitable windows and space for detectors are left for experiments using harmonics as a probe as well as the possibility of measuring optical absorption of the probe pulses. A table-top supercontinuum probe system [17,18] will be installed for collecting ultrafast optical absorption and reflectivity data in a wide range of wavelengths in a single shot.…”

Ab initioabsorption spectrum of NiO combining molecular dynamics with the embedded cluster approach in a discrete reaction field

“…Note that this decomposition strategy can also be used to unravel the optical absorption spectra of more complex materials for which the nature of the excited electronic states is less clear. [108][109][110] On the other hand, the high absorption plateau extending over 4 eV is clearly overestimated by ∼2 eV. This band is mainly formed by dipole and spin-allowed LMCT processes where an electron is transferred from an O(2p) orbital to a 3d(e g )-like orbital on Ni.…”

Approach to a stationary state in a driven Hubbard model coupled to a thermostat

“…The theoretical investigation of out-of-equilibrium strongly correlated quantum systems recently generated a tremendous interest, stimulated by the development of novel experimental techniques, which allow to explore transport properties of correlated materials in a non-equilibrium regime, [1][2][3] notwithstanding the recent achievements in the field of optically trapped cold-atoms. These experimental advances challenge the theory to develop suitable new methods to describe how a strongly correlated materials evolves when an external field pushes it out-of-equilibrium.…”