  Understanding the effects of spin-orbit coupling (SOC) and many-body
interactions on spin transport is important in condensed matter physics and
spintronics. This topic has been intensively studied for spin carriers such as
electrons but barely explored for charge-neutral bosonic quasiparticles
(including their condensates), which hold promises for coherent spin transport
over macroscopic distances. Here, we explore the effects of synthetic SOC
(induced by optical Raman coupling) and atomic interactions on the spin
transport in an atomic Bose-Einstein condensate (BEC), where the spin-dipole
mode (SDM, actuated by quenching the Raman coupling) of two interacting spin
components constitutes an alternating spin current. We experimentally observe
that SOC significantly enhances the SDM damping while reducing the
thermalization (the reduction of the condensate fraction). We also observe
generation of BEC collective excitations such as shape oscillations. Our theory
reveals that the SOC-modified interference, immiscibility, and interaction
between the spin components can play crucial roles in spin transport.
