Nonequilibrium crossover in the supercritical region from quench dynamics

TL;DR

This paper introduces a nonequilibrium dynamical method to identify a new crossover line in the supercritical region of a holographic superfluid model, based on invasion velocity behavior after a quench.

Contribution

It proposes a novel nonequilibrium dynamical approach to characterize supercritical subphases, revealing a new crossover line distinct from classical lines.

Findings

Invasion velocity shows a clear turning point as a function of quench endpoint.

The new crossover line encodes thermodynamic and kinetic information.

The approach offers a dynamical perspective on supercritical subphases.

Abstract

Distinguishing different subphases in the supercritical region is a fundamental issue in statistical physics and condensed matter physics. Traditional approaches mainly rely on static thermodynamic response functions or equilibrium correlation functions, which are inherently confined to quasi-static processes. In this work, we adopt a nonequilibrium dynamical perspective to investigate the evolution of a holographic superfluid model following a rapid quench across the critical point. We find that the invasion phenomenon induced by topological defects persists in the supercritical region, and the invasion velocity exhibits a clear turning point as a function of the quench endpoint $\rho_f$. This turning point defines a new nonequilibrium supercritical crossover line. In contrast to the classical Widom line or Frenkel line, this new crossover line encodes both thermodynamic information and kinetic information, reflecting the dynamical nature of the supercritical region under nonequilibrium conditions. This study provides a novel nonequilibrium dynamical approach for characterizing supercritical subphases.