Nonthermal antiferromagnetic order and nonequilibrium criticality in the Hubbard model

TL;DR

This paper investigates nonequilibrium dynamical phase transitions in the Hubbard model, revealing nonthermal antiferromagnetic order and critical behavior that differ from thermal expectations, with implications for understanding relaxation dynamics.

Contribution

It uncovers nonthermal antiferromagnetic states and critical points in the Hubbard model driven by interaction quenches, highlighting new nonequilibrium phenomena.

Findings

Identification of two dynamical transition points with distinct relaxation behaviors

Observation of nonthermal antiferromagnetic order above the thermal critical temperature

Critical slowing down of amplitude mode frequency near the nonthermal critical point

Abstract

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. The frequency of the amplitude mode extrapolates to zero as one approaches the nonthermal (quasi)critical point, and thermalization is significantly delayed by the trapping in the nonthermal state. A slow relaxation of the nonthermal order is followed by a faster thermalization process.