Instabilities in binary mixtures of one-dimensional quantum degenerate gases

TL;DR

This paper investigates the stability and phase behavior of one-dimensional quantum degenerate binary mixtures, revealing conditions for collapse, demixing, and pairing fluctuations, with implications for continuum and lattice systems.

Contribution

It identifies specific instabilities and pairing phenomena in 1D binary quantum gases, extending understanding of their phase diagrams and correlations.

Findings

Strong attraction causes collapse or pairing.

Strong repulsion leads to demixing.

Equal-density impenetrable boson mixtures develop a gap.

Abstract

We show that one-dimensional binary mixtures of bosons or of a boson and a spin-polarized fermion are Luttinger liquids with the following instabilities: i) For different particle densities, strong attraction between the mixture components leads to collapse, while strong repulsion leads to demixing, ii) For a low-density mixture of two gases of impenetrable bosons (or a spin-polarized fermion and an impenetrable boson) of equal densities, the system develops a gap and exhibits enhanced pairing fluctuations when there is attraction between the components. In the boson-fermion mixture, the pairing fluctuations occur at finite momentum. Our conclusions apply to mixtures both on the continuum and on optical lattices away from integer or fractional commensurability.