School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Department of Physics, The University of Texas at Dallas, Richardson, TX, 75080, USA.
Nat Commun. 2019 Jan 22;10(1):375. doi: 10.1038/s41467-018-08119-4.
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.
理解自旋轨道耦合（SOC）和多体相互作用对自旋输运的影响在凝聚态物理和自旋电子学中非常重要。这个课题已经在电子等自旋载体上得到了深入研究，但对于电荷中性玻色准粒子（包括它们的凝聚体）几乎没有探索，后者有望实现宏观距离上的相干自旋输运。在这里，我们研究了通过光学拉曼耦合诱导的合成 SOC 和原子相互作用对原子玻色-爱因斯坦凝聚体（BEC）中自旋输运的影响，其中两个相互作用的自旋分量的自旋偶极模式（SDM，通过猝灭拉曼耦合来实现）构成了交替的自旋电流。我们实验观察到 SOC 显著增强了 SDM 的阻尼，同时减少了热化（凝聚分数的减少）。我们还观察到 BEC 集体激发的产生，如形状振荡。我们的理论揭示了 SOC 修正的干涉、不混溶性和自旋分量之间的相互作用可以在自旋输运中发挥关键作用。
