Quenching to unitarity: Quantum dynamics in a 3D Bose gas

TL;DR

This paper investigates the non-equilibrium dynamics of a 3D Bose gas quenched to unitarity, combining variational, two-body, and experimental insights to understand momentum distribution, Tan's contact, and loss rates.

Contribution

It introduces a comprehensive analysis of Bose gas dynamics at unitarity using multiple methods, including a variational approach and analytic two-body models, to predict momentum evolution and loss behavior.

Findings

Tan's contact increases linearly at short times.

Large momentum modes have longer lifetimes than the overall gas.

The dynamics are well captured by the combined approaches.

Abstract

We study the dynamics of a dilute Bose gas at zero temperature following a sudden quench of the scattering length from a noninteracting Bose condensate to unitarity (infinite scattering length). We apply three complementary approaches to understand the momentum distribution and loss rates. First, using a time-dependent variational ansatz for the many-body state, we calculate the dynamics of the momentum distribution. Second, we demonstrate that, at short times and large momenta compared to those set by the density, the physics can be well understood within a simple, analytic two-body model. We derive a quantitative prediction for the evolution of Tan's contact, which increases linearly at short times. We also study the three-body losses at finite densities. Consistent with experiments, we observe lifetimes which are long compared to the dynamics of large momentum modes.