Effective metal-insulator nonequilibrium quantum phase transition in the Su-Schrieffer-Heeger model

We consider the steady-state behavior of observables in the Su-Schrieffer-Heeger (SSH) model and in the one-dimensional transverse field quantum Ising model after a sudden quantum quench of the parameter controlling the gap. In the thermodynamic limit, and for times t -> infinity, we find nonanalyticities even in simple local observables as a function of the quench parameter, that is, a nonequilibrium quantum phase transition. We trace the appearance of this nonequilibrium quantum phase transition to an effective metal-insulator transition which occurs on the level of the generalized Gibbs ensemble (describing the steady state of the equilibrated system). Studying whether these transitions are robust, we find, in the paradigmatic case of the SSH model, that they persist for both quantum quench protocols of finite duration in time as well as thermal initial states, while they are washed out in the presence of fermion-fermion interactions and for finite system size.