Long-time behavior of the momentum distribution during the sudden expansion of a spin-imbalanced Fermi gas in one dimension

TL;DR

This paper investigates the long-term momentum distribution behavior of a spin-imbalanced Fermi gas in one dimension after sudden expansion, revealing rapid approach to stationary states and loss of FFLO correlations due to quantum distillation.

Contribution

It demonstrates how stationary momentum distributions relate to integrals of motion and explains the loss of FFLO correlations during expansion in an integrable quantum system.

Findings

Momentum distributions quickly become stationary due to quantum distillation.

FFLO correlations are lost during the expansion process.

Stationary distributions can be linked to integrals of motion.

Abstract

We study the sudden expansion of spin-imbalanced ultracold lattice fermions with attractive interactions in one dimension after turning off the longitudinal confining potential. We show that the momentum distribution functions of majority and minority fermions approach stationary values quickly due to a quantum distillation mechanism that results in a spatial separation of pairs and majority fermions. As a consequence, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) correlations are lost during the expansion. Furthermore, we argue that the shape of the stationary momentum distribution functions can be understood by relating them to the integrals of motion in this integrable quantum system. We discuss our results in the context of proposals to observe FFLO correlations, related to recent experiments by Liao et al., Nature 467, 567 (2010).