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Entanglement exhibits universal behavior near the ground state of a critical point where correlations
are long-ranged and the thermodynamic entropy is vanishing. On the other hand, a quantum
quench imparts extensive energy and results in a build-up of entropy, hence no critical behavior
is expected at a long-time stationary state. In our work, we present a new paradigm in the quench dynamics of
integrable spin chains which exhibit a ground-state order-disorder phase transition at a critical line.
Specifically, we perform a quench along the critical line and observe a surprising behavior: While the
long-time stationary state displays a typical volume-law entanglement and exponential decay of two-point
correlations, a quantum criticality is hidden in higher-order correlations. These quantum critical correlations
are captured via quantum information measures such as mutual information and logarithmic negativity.
We attribute the emerging criticality to the vanishing effective temperature of the soft mode in spite of the
quench. We extend this study to system near-integrability and demonstrate the continued existence of
quantum critical behavior in the near-integrable limit. |