Photo-induced insulator-metal transition in paramagnetic (V_1-xCr_x)_2O_3

Pump-probe experiments with femtosecond time resolution allow to disentangle the electronic dynamics from the lattice response and thus provide valuable insights into the non-equilibrium behavior of correlated materials. In Cr-doped V_2O_3, a multi-orbital Mott-Hubbard material which has been intensively investigated for decades, time-resolved experiments reported a photo-induced insulator-metal transition leading to a transient metal state with nonthermal properties. Here, we combine non-equilibrium dynamical mean-field theory with realistic first principles modeling to simulate the ultrafast response of this material to a laser excitation. Our calculations reproduce the insulating initial state, with orbital occupations in agreement with experiment, and reveal an ultrafast pump-induced gap filling associated with a charge reshuffling between the e_g^π and a_1g orbitals. However, in contrast to the related compound VO_2, the electronic system thermalizes within a few tens of femtoseconds and we find no evidence for the existence of a metastable nonthermal metal. This suggests that the reported nonthermal behavior in the experiments may be associated with the mismatch between the electronic and lattice temperatures.