Hidden quantum criticality in quench dynamics of the XY model

We investigate the stationary states of the one-dimensional anisotropic XY model upon a sudden quench. We find that quenches along the critical line display surprising behavior: While the long-time stationary state shows a typical volume-law entanglement and exponential decay of two-point correlations, a subleading logarithmic term emerges indicating that mutual information is critical. We find the same behavior in logarithmic negativity, indicating quantum criticality yet at finite energy density. We attribute this behavior to the vanishing effective temperature of the soft mode in spite of the quench. Finally, we discuss experimental platforms where this physics can be observed experimentally.