Superfluidity and phase transitions in a resonant Bose gas

TL;DR

This paper investigates the phase diagram, thermodynamics, and excitation spectra of a resonant Bose gas, revealing two superfluid phases and a quantum phase transition between them.

Contribution

It introduces the existence of two distinct superfluid phases in a resonant Bose gas and characterizes the quantum Ising transition between atomic and molecular superfluids.

Findings

Identification of atomic and molecular superfluid phases.

Molecular superfluid undergoes a quantum Ising transition to atomic superfluid.

Distinct thermodynamic signatures and vortex properties for each phase.

Abstract

The atomic Bose gas is studied across a Feshbach resonance, mapping out its phase diagram, and computing its thermodynamics and excitation spectra. It is shown that such a degenerate gas admits two distinct atomic and molecular superfluid phases, with the latter distinguished by the absence of atomic off-diagonal long-range order, gapped atomic excitations, and deconfined atomic pi-vortices. The properties of the molecular superfluid are explored, and it is shown that across a Feshbach resonance it undergoes a quantum Ising transition to the atomic superfluid, where both atoms and molecules are condensed. In addition to its distinct thermodynamic signatures and deconfined half-vortices, in a trap a molecular superfluid should be identifiable by the absence of an atomic condensate peak and the presence of a molecular one.