Phase Separation Dynamics Induced by an Interaction Quench of a Correlated Fermi-Fermi Mixture in a Double Well

TL;DR

This paper investigates the dynamics of phase separation in ultracold Fermi-Fermi mixtures after an interaction quench, revealing the crucial role of correlations and many-body effects in the process.

Contribution

It demonstrates that many-body correlations prevent phase separation predicted by Hartree-Fock, highlighting the importance of beyond mean-field effects in ultracold mixtures.

Findings

Interspecies phase separation occurs in Hartree-Fock but not in many-body treatment.

Strong correlations induce intrawell fragmentation and anti-ferromagnetic-like behavior.

Single-shot measurements can reveal the correlation-driven phase separation.

Abstract

We explore the interspecies interaction quench dynamics of ultracold spin-polarized few-body mass balanced Fermi-Fermi mixtures confined in a double-well with an emphasis on the beyond Hartree-Fock correlation effects. It is shown that the ground state of particle imbalanced mixtures exhibits a symmetry breaking of the single-particle density for strong interactions in the Hartree-Fock limit, which is altered within the many-body approach. Quenching the interspecies repulsion towards the strongly interacting regime the two species phase separate within the Hartree-Fock approximation while remaining miscible in the many-body treatment. Despite their miscible character on the one-body level the two species are found to be strongly correlated and exhibit a phase separation on the two-body level that suggests the anti-ferromagnetic like behavior of the few-body mixture. For particle balanced mixtures we show that an intrawell fragmentation (filamentation) of the density occurs both for the ground state as well as upon quenching from weak to strong interactions, a result that is exclusively caused by the presence of strong correlations. Inspecting the two-body correlations a phase separation of the two species is unveiled being a precursor towards an anti-ferromagnetic state. Finally, we simulate in-situ single-shot measurements and showcase how our findings can be retrieved by averaging over a sample of single-shot images.