Emergence of a new pair-coherent phase in many-body quenches of repulsive bosons

TL;DR

This paper studies how a sudden change in interaction strength in a two-mode bosonic system leads to a novel pair-coherent phase in an excited state, revealing complex coherence dynamics beyond ground-state predictions.

Contribution

It uncovers a new pair-coherent phase emerging during dynamical quenches in an interacting bosonic system, highlighting non-trivial excited-state coherence properties.

Findings

A new pair-coherent phase appears after quenches from negative to positive coupling.

The phase is non-fragmented despite ground-state expectations.

The emergence occurs in excited states during rapid transitions.

Abstract

We investigate the dynamical mode population statistics and associated first- and second-order coherence of an interacting bosonic two-mode model when the pair-exchange coupling is quenched from negative to positive values. It is shown that for moderately rapid second-order transitions, a new pair-coherent phase emerges on the positive coupling side in an excited state, which is not fragmented as the ground-state single-particle density matrix would prescribe it to be.