Orbital-selective thermalization plateau in the mass imbalanced Hubbard model

We use time-dependent non-equilibrium dynamical mean-field theory with weak-coupling auxiliary-field continuous time quantum Monte Carlo as an impurity solver to study the thermalization behavior of the mass-imbalanced single-band Hubbard model after a quench of the Coulomb interaction from the non-interacting limit to a finite positive value. By contrast, when the Coulomb interaction in our model is increased under equilibrium conditions, the quasi-particle weight for spin-up and spin-down (the mass imbalance) electrons approach zero simultaneously, indicating the absence of an orbital selective Mott transition. Our out-of-equilibrium study suggests that there exists a time window where an orbital selective dynamical phase transition occurs. The dynamical phase transition is characterized by the relaxation behavior of energy (kinetic and Coulomb interaction) and the spin-resolved momentum-dependent occupation. To make connection with possible experiments, we calculate the spin-resolved two-time optical conductivity, which confirms the orbital-selective thermalization plateau. We find the time window for the orbital selective dynamical phase transition grows as the mass imbalance increases.