Quantum gas-liquid condensation in an attractive Bose gas

TL;DR

This paper investigates gas-liquid condensation in an attractive Bose gas, revealing a quantum-mechanical analogue to classical GLC driven by Bose-statistical coherence, occurring before Bose-Einstein condensation at low temperatures.

Contribution

It introduces a quantum GLC mechanism in attractive Bose gases, showing divergence of the grand partition function due to Bose coherence before BEC.

Findings

Quantum GLC occurs prior to BEC at low temperatures.

Weak attractive forces can trigger quantum GLC.

Analysis relevant to low-pressure helium 4 gas.

Abstract

Gas-liquid condensation (GLC) in an attractive Bose gas is studied on the basis of statistical mechanics. Using some results in combinatorial mathematics, the following are derived: (1) With decreasing temperature, the Bose-statistical coherence grows in the many-body wave function, which gives rise to the divergence of the grand partition function prior to Bose-Einstein condensation. It is a quantum-mechanical analogue to the GLC in a classical gas (quantum GLC). (2) This GLC is triggered by the bosons with zero momentum. Compared with the classical GLC, an incomparably weaker attractive force creates it. For the system showing the quantum GLC, we discuss a cold helium 4 gas at sufficiently low pressure.