Anisotropic relaxation dynamics in a dipolar Fermi gas driven out of equilibrium

TL;DR

This study demonstrates significant anisotropic rethermalization dynamics in an ultracold dipolar Fermi gas of erbium atoms, confirming theoretical predictions and revealing that Pauli blocking does not affect collision suppression by dipole orientation.

Contribution

It provides the first experimental observation of anisotropic dipolar scattering effects in a Fermi gas, aligning with recent theoretical models.

Findings

Strong angular dependence of thermal relaxation dynamics observed.

Rethermalization rate remains unaffected by dipole orientation despite Pauli blocking.

Experimental results agree well with theoretical predictions.

Abstract

We report on the observation of a large anisotropy in the rethermalization dynamics of an ultracold dipolar Fermi gas driven out of equilibrium. Our system consists of an ultracold sample of strongly magnetic $^{167}$Er fermions, spin-polarized in the lowest Zeeman sublevel. In this system, elastic collisions arise purely from universal dipolar scattering. Based on cross-dimensional rethermalization experiments, we observe a strong anisotropy of the scattering, which manifests itself in a large angular dependence of the thermal relaxation dynamics. Our result is in very good agreement with recent theoretical predictions. Furthermore, we measure the rethermalization rate as a function of temperature for different angles and find that the suppression of collisions by Pauli blocking is not influenced by the dipole orientation.