Naoto Tsuji, Martin Eckstein, Philipp Werner
We study dynamical phase transitions from antiferromagnetic to paramagnetic states driven by an interaction quench in the fermionic Hubbard model using the nonequilibrium dynamical mean-field theory. We identify two dynamical transition points where the relaxation behavior qualitatively changes: one corresponds to the thermal phase transition at which the order parameter decays critically slowly in a power law $\propto t^{-1/2}$, and the other is connected to the existence of nonthermal antiferromagnetic order in systems with effective temperature above the thermal critical temperature. Thermalization is significantly delayed by the trapping in the nonthermal state, and the frequency of the amplitude mode extrapolates to zero as one approaches the nonthermal (quasi-)critical point. The slow relaxation of the nonthermal order is followed by a faster thermalization process.
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http://arxiv.org/abs/1210.0133
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