Nonequilibrium pump-probe photoexcitation as a tool for analyzing unoccupied equilibrium states of correlated electrons

Relaxation of electrons in a Hubbard ring coupled to a dissipative bosonic bath is studied to simulate the pump-probe photoemission measurement. From this insight, we propose an experimental method of eliciting the unoccupied part of single-particle spectra at the equilibrium of doped Mott insulators. We reveal first that the effective temperatures of distribution functions and electronic spectra are different during the relaxation, which makes the frequently employed thermalization picture inappropriate. Contrary to the conventional analysis, we show that the unoccupied spectra at equilibrium can be detected as the states that relax faster.