Universal Scaling Laws in the Dynamics of a Homogeneous Unitary Bose Gas

TL;DR

This paper investigates the universal scaling laws governing the dynamics of a homogeneous Bose gas at unitarity, revealing how particle loss and correlations evolve during the crossover from degenerate to thermal regimes after an interaction quench.

Contribution

It introduces universal scaling laws for particle loss and correlation dynamics in a unitary Bose gas, observed during a quench and crossover regimes.

Findings

Particle-loss rate scales as N^{2/3} in degenerate regime.

Particle-loss rate scales as N^{26/9} in thermal regime.

Universal temporal scaling of correlations with gas density.

Abstract

We study the dynamics of an initially degenerate homogeneous Bose gas after an interaction quench to the unitary regime at a magnetic Feshbach resonance. As the cloud decays and heats, it exhibits a crossover from degenerate- to thermal-gas behaviour, both of which are characterised by universal scaling laws linking the particle-loss rate to the total atom number $N$. In the degenerate and thermal regimes the per-particle loss rate is $\propto N^{2/3}$ and $N^{26/9}$, respectively. The crossover occurs at a universal kinetic energy per particle and at a universal time after the quench, in units of energy and time set by the gas density. By slowly sweeping the magnetic field away from the resonance and creating a mixture of atoms and molecules, we also map out the dynamics of correlations in the unitary gas, which display a universal temporal scaling with the gas density, and reach a steady state while the gas is still degenerate.