Quench-induced delocalization

TL;DR

This paper studies how a sudden removal of short-range interactions in a quantum system causes wave packet delocalization, with implications for disordered systems and the role of high-momentum states.

Contribution

It demonstrates that interaction quenches induce delocalization via Tan's relations and explores the effects of finite interaction range on state coupling.

Findings

Interaction quench leads to wave packet delocalization.

High-momentum tail of the distribution plays a key role.

Disordered systems become more delocalized after an interaction quench.

Abstract

We consider the evolution of an initially localized wave packet after a sudden change in the Hamiltonian, i.e.\ a quench. When both bound and scattering eigenstates exist in the post-quench Hamiltonian, one might expect partial delocalization of the wave packet to ensue. Here we show that if the quench consists of a sudden switching-off of short-range inter-particle interactions, then Tan's universal relations guarantee delocalization through the high-momentum tail of the momentum distribution. Furthermore, we consider the influence of the range of the interaction and show how a finite range alters the coupling to highly excited states. We illustrate our results using numerical simulations of externally trapped particles in one dimension. If the external potential is both disordered and correlated, then the interaction quench leads to transport via delocalized states, showing that localization in disordered systems is sensitive to non-adiabatic changes in the interactions between particles.