Liquid-solid transitions in the three-body hard-core model

TL;DR

This paper maps the phase diagram of a three-body hard-core model, revealing unique solid and liquid phases in two and three dimensions, with implications for quantum systems like the unitary Bose gas.

Contribution

It introduces a generalized three-body hard-core model and characterizes its phase diagram in two and three dimensions, highlighting novel phase behaviors.

Findings

Two-dimensional model has a liquid phase and a dimer solid phase.

Three-dimensional model features isolated atoms in a simple-hexagonal lattice.

Solid phases in both dimensions differ from traditional hard-sphere models.

Abstract

We determine the phase diagram for a generalisation of two-and three-dimensional hard spheres: a classical system with three-body interactions realised as a hard cut-off on the mean-square distance for each triplet of particles. Quantum versions of this model are important in the context of the unitary Bose gas, which is currently under close theoretical and experimental scrutiny. In two dimensions, the three-body hard-core model possesses a conventional atomic liquid phase and a peculiar solid phase formed by dimers. These dimers interact effectively as hard disks. In three dimensions, the solid phase consists of isolated atoms that arrange in a simple-hexagonal lattice.