Spin Transport in Polaronic and Superfluid Fermi Gases

TL;DR

This study investigates spin transport in ultracold fermionic lithium-6 gases near a Feshbach resonance, revealing strong damping of spin modes even in superfluid conditions, advancing understanding of spin dynamics in quantum gases.

Contribution

It provides the first measurements of spin dipole mode damping in polaronic and superfluid Fermi gases, highlighting the effects of strong interactions and superfluidity on spin transport.

Findings

Strong, unitarity-limited damping of spin dipole modes observed.

Damped spin flow persists below the superfluid transition.

Spin transport is significantly affected by interactions and superfluidity.

Abstract

We present measurements of spin transport in ultracold gases of fermionic lithium-6 in a mixture of two spin states at a Feshbach resonance. In particular, we study the spin dipole mode, where the two spin components are displaced from each other against a harmonic restoring force. We prepare a highly-imbalanced, or polaronic, spin mixture with a spin dipole excitation and observe strong, unitarity limited damping of the spin dipole mode. In gases with small spin imbalance, below the Pauli limit for superfluidity, we observe strongly damped spin flow despite the presence of a superfluid core.