Coherence Spreading Law in Quenched Homogeneous Bose Gases

Abstract

We investigate nonequilibrium coherence spreading in quenched homogeneous bosonic gases both analytically and numerically. Our ensemble-averaged Gross-Pitaevskii trajectory approach and kinetic analysis confirm the linear-in-time growth of the squared coherence length, and explicitly give the spreading-law dependence on the ratio of initial energy to healing energy. When the ratio is relatively small, the squared coherence length grows at a universal rate determined by the ratio of Planck's constant to the particle mass, insensitive to interaction strength and initial momentum distributions. However, our further calculations uncover fundamental limitations to such universality and establish its phase boundaries governed by low system energies, weak interparticle interactions and many-body integrability. Our theory fully reproduces the key experimental signatures and resolves the puzzle of the dynamical origin of the recently observed universal coherence-spreading speed limit [Nature 647, 608-612 (2025)]. Going beyond existing experimental observations, we provide some testable predictions for ultracold-atom experiments and clarify the conditions for the emergence of universal coherent dynamics in nonequilibrium bosonic many-body systems.