Multi-particle composites in density-imbalanced quantum fluids

TL;DR

This paper studies one-dimensional two-component quantum gases with density imbalance, revealing that strong mass asymmetry and rational density ratios lead to a gapped phase with composite particle order, affecting superconducting correlations.

Contribution

It demonstrates that density imbalance and mass asymmetry induce a gapped phase with composite order in two-component quantum fluids, supported by numerical simulations.

Findings

Gapped phase occurs at rational density ratios with strong mass asymmetry.

Composite particle ordering emerges in the gapped phase.

Superconducting correlations are suppressed in the gapped regime.

Abstract

We consider two-component one-dimensional quantum gases with density imbalance. While generically such fluids are two-component Luttinger liquids, we show that if the ratio of the densities is a rational number, p/q, and mass asymmetry between components is sufficiently strong, one of the two eigenmodes acquires a gap. The gapped phase corresponds to (algebraic) ordering of (p+q)-particle composites. In particular, for attractive mixtures, this implies that the superconducting correlations are destroyed. We illustrate our predictions by numerical simulations of the fermionic Hubbard model with hopping asymmetry.