Nonequilibrium dynamics of an ultracold dipolar gas

TL;DR

This paper investigates the non-equilibrium behavior of ultracold dipolar gases, revealing how dipole orientation influences relaxation and damping, with simulations aligning well with experimental data and highlighting collision-dominated regimes.

Contribution

It introduces a Monte Carlo simulation approach to study dipolar gas dynamics, emphasizing the role of anisotropic collisions in relaxation processes.

Findings

Relaxation and damping rates depend strongly on dipole orientation.

Simulation results agree with recent experimental observations.

Collision processes dominate over mean-field effects in certain regimes.

Abstract

We study the relaxation and damping dynamics of an ultracold, but not quantum degenerate, gas consisting of dipolar particles. These simulations are performed using a direct simulation Monte Carlo method and employing the highly anisotropic differential cross section of dipoles in the Wigner threshold regime. We find that both cross-dimensional relaxation and damping of breathing modes occur at rates that are strongly dependent on the orientation of the dipole moments relative to the trap axis. The relaxation simulations are in excellent agreement with recent experimental results in erbium. The results direct our interest toward a less explored regime in dipolar gases where interactions are dominated by collision processes rather than mean-field interactions.