Ground state of a resonantly interacting Bose gas

TL;DR

This paper develops an improved theoretical approach to determine the ground state properties of a resonantly interacting Bose gas, including the chemical potential, Tan's contact, and condensate fraction, near a Feshbach resonance.

Contribution

It introduces a variational Jastrow ansatz combined with the hypernetted-chain approximation to go beyond mean-field theory for Bose gases at unitarity.

Findings

Analytic computation of the chemical potential at unitarity.

Calculation of Tan's contact and condensate fraction from the wave function.

Enhanced understanding of ground state properties of resonantly interacting Bose gases.

Abstract

We show that a two-channel mean-field theory for a Bose gas near a Feshbach resonance allows for an analytic computation of the chemical potential, and therefore the universal constant \beta, at unitarity. To improve on this mean-field theory, which physically neglects condensate depletion, we study a variational Jastrow ansatz for the ground-state wave function and use the hypernetted-chain approximation to minimize the energy for all positive values of the scattering length. We also show that other important physical quantities such as Tan's contact and the condensate fraction can be directly obtained from this approach.