Ballistic quench-induced correlation waves in ultracold gases

TL;DR

This paper studies how rapid changes in interaction strength in ultracold gases create propagating correlation waves, revealing universal behaviors and implications for transport in optical lattices.

Contribution

The authors derive universal analytic results describing correlation wave dynamics post-quench, linking initial contact to wave strength and analyzing ballistic contributions in momentum tails.

Findings

Correlation waves propagate rapidly after a quench.

Universal analytic expressions describe the wave dynamics.

Ballistic contributions affect momentum distribution tails.

Abstract

We investigate the wave packet dynamics of a pair of particles that undergoes a rapid change of scattering length. The short-range interactions are modeled in the zero-range limit, where the quench is accomplished by switching the boundary condition of the wave function at vanishing particle separation. This generates a correlation wave that propagates rapidly to nonzero particle separations. We have derived universal, analytic results for this process that lead to a simple phase-space picture of the quench-induced scattering. Intuitively, the strength of the correlation wave relates to the initial contact of the system. We find that, in one spatial dimension, the $k^{-4}$ tail of the momentum distribution contains a ballistic contribution that does not originate from short-range pair correlations, and a similar conclusion can hold in other dimensionalities depending on the quench protocol. We examine the resultant quench-induced transport in an optical lattice in 1D, and a semiclassical treatment is found to give quantitatively accurate estimates for the transport probabilities.