  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.
