Liquid-gas transition and coexistence in ground-state bosons with spin twist

TL;DR

This paper explores how a spin twist in ground-state bosons can facilitate a liquid-gas transition and coexistence, enabling control over phase behavior through spin polarization mismatch.

Contribution

It introduces the concept of spin twist as a mechanism to stabilize the gas phase and induce liquid-gas transition in spinor bosons, with practical implementation in Rabi-coupled binary bosons.

Findings

Spin twist creates effective repulsion, stabilizing the gas phase.

Liquid-gas transition can be tuned via Rabi coupling and magnetic detuning.

Coexistence manifests as a discontinuous density profile in traps.

Abstract

We study the thermodynamic liquid-gas transition and coexistence (LGTC) for ground-state bosons under contact interactions. We find that the LGTC can be facilitated by the mismatch of spin polarization, dubbed "spin twist," between single-particle and interaction channels of bosons with spin degrees of freedom. Such a spin twist uniquely stabilizes the gas phase by creating an effective repulsion for low-density bosons, thereby enabling LGTC in the presence of a quantum droplet at a much larger density. We have demonstrated the scheme for binary bosons subject to Rabi coupling and magnetic detuning, where the liquid-gas transition can be conveniently tuned and their coexistence can be characterized by a discontinuous density profile in a harmonic trap. The spin twist scheme for LGTC can be generalized to a wide class of quantum systems with competing single-particle and interaction orders.