Properties of a Dilute Bose Gas near a Feshbach Resonance

TL;DR

This paper investigates the properties of a dilute Bose gas near a Feshbach resonance at zero temperature, highlighting the coexistence of atomic and molecular condensates, excitation spectra, and enhanced three-body recombination rates.

Contribution

It provides a theoretical analysis of atomic and molecular excitations and decay processes in a Bose gas near a Feshbach resonance, aligning with recent experimental findings.

Findings

Molecular to atom density ratio is π na^3.

Atomic excitations are gapless, molecular excitations have finite energy.

Three-body recombination rate is significantly increased near resonance.

Abstract

In this paper, properties of a homogeneous Bose gas with a Feshbach resonance are studied in the dilute region at zero temperature. The stationary state contains condensations of atoms and molecules. The ratio of the molecule density to the atom density is $\pi na^3$. There are two types of excitations, molecular excitations and atomic excitations. Atomic excitations are gapless, consistent with the traditional theory of a dilute Bose gas. The molecular excitation energy is finite in the long wavelength limit as observed in recent experiments on $^{85}$Rb. In addition, the decay process of the condensate is studied. The coefficient of the three-body recombination rate is about 140 times larger than that of a Bose gas without a Feshbach resonance, in reasonably good agreement with the experiment on $^{23}$Na.