We use time-dependent nonequilibrium 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 noninteracting limit to a finite positive value. When the Coulomb interaction in our model is increased under equilibrium conditions, the quasiparticle weights for spin-up and spin-down (the mass imbalance) electrons approach zero simultaneously, indicating the absence of a spin-selective Mott transition. By contrast, our out-of-equilibrium study of the mass-imbalanced Hubbard model suggests that there exists the spin-selective dynamical phase transition (one spin orientation undergoes a fast thermalization at its critical Coulomb interaction strength while the other spin orientation shows prethermalization behavior). The spin-selective dynamical phase transition is characterized by the relaxation behavior of the spin-resolved kinetic energy and the spin-resolved momentum-dependent occupation. To connect with possible experiments, we calculate the spin-resolved two-time optical conductivity, which confirms the spin-selective thermalization plateau. We find that the critical Coulomb interaction of each spin orientation for the spin-selective thermalization grows as the mass imbalance decreases.

• Received 7 August 2017
• Revised 6 October 2017

DOI:https://doi.org/10.1103/PhysRevB.96.165151