Non-equilibrium spin dynamics in a trapped Fermi gas with effective spin-orbit interaction

TL;DR

This paper investigates non-equilibrium spin dynamics in a trapped Fermi gas with effective spin-orbit coupling induced by laser fields, revealing periodic spin echoes and effects of trap asymmetry.

Contribution

It introduces a model for spin dynamics in a trapped Fermi gas with laser-induced spin-orbit coupling and analyzes non-equilibrium behavior including spin echoes.

Findings

Spin polarization exhibits periodic echoes at the trap frequency.

Trap asymmetry suppresses the amplitude of spin echoes.

The proposed setup is feasible for experimental observation.

Abstract

We consider a trapped atomic system in the presence of spatially varying laser fields. The laser-atom interaction generates a pseudospin degree of freedom (referred to simply as spin) and leads to an effective spin-orbit coupling for the fermions in the trap. Reflections of the fermions from the trap boundaries provide a physical mechanism for effective momentum relaxation and non-trivial spin dynamics due to the emergent spin-orbit coupling. We explicitly consider evolution of an initially spin-polarized Fermi gas in a two-dimensional harmonic trap and derive non-equilibrium behavior of the spin polarization. It shows periodic echoes with a frequency equal to the harmonic trapping frequency. Perturbations, such as an asymmetry of the trap, lead to the suppression of the spin echo amplitudes. We discuss a possible experimental setup to observe spin dynamics and provide numerical estimates of relevant parameters.