Spin-orbit-coupled Bose-Einstein condensates
Spin-orbit-coupled Bose-Einstein condensates
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DOI：
10.1038/nature09887
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发表时间：
2011-03-03
期刊：
影响因子：
64.8
通讯作者：
Spielman, I. B.
中科院分区：
文献类型：
--
作者：
Lin, Y. -J.;Jimenez-Garcia, K.;Spielman, I. B.
自旋-轨道（SO）耦合-量子粒子的自旋和动量之间的相互作用-在物理系统中无处不在。在凝聚态系统中，SO耦合对于自旋霍尔效应（1，2）和拓扑绝缘体（3-5）至关重要;它有助于GaAs等材料的电子特性，并且对于自旋电子器件（6）很重要。超冷原子的量子多体系统可以通过实验精确控制，因此似乎提供了一个研究SO耦合的理想平台。虽然原子的内禀SO耦合影响其电子结构，但它并不导致原子的自旋与质心运动之间的耦合。在这里，我们通过用一对激光器（9）修饰两个原子自旋态，在中性原子玻色-爱因斯坦凝聚体中设计SO耦合（具有相等的Rashba（7）和Dresselhaus（8）强度）。这种耦合以前没有在超冷原子气体或任何玻色子系统中实现过。此外，在激光耦合的存在下，两个修饰的原子自旋状态之间的相互作用被修改，驱动从空间自旋混合状态（激光关闭）到相分离状态（高于临界激光强度）的量子相变。我们开发了一个多体理论，提供了定量的协议与观察到的过渡位置。工程SO耦合-同样适用于玻色子和费米子-设置阶段实现拓扑绝缘体中的费米子中性原子系统。
Spin-orbit (SO) coupling-the interaction between a quantum particle's spin and its momentum-is ubiquitous in physical systems. In condensed matter systems, SO coupling is crucial for the spin-Hall effect(1,2) and topological insulators(3-5); it contributes to the electronic properties of materials such as GaAs, and is important for spintronic devices(6). Quantum many-body systems of ultracold atoms can be precisely controlled experimentally, and would therefore seem to provide an ideal platform on which to study SO coupling. Although an atom's intrinsic SO coupling affects its electronic structure, it does not lead to coupling between the spin and the centre-of-mass motion of the atom. Here, we engineer SO coupling (with equal Rashba(7) and Dresselhaus(8) strengths) in a neutral atomic Bose-Einstein condensate by dressing two atomic spin states with a pair of lasers(9). Such coupling has not been realized previously for ultracold atomic gases, or indeed any bosonic system. Furthermore, in the presence of the laser coupling, the interactions between the two dressed atomic spin states are modified, driving a quantum phase transition from a spatially spin-mixed state (lasers off) to a phase-separated state (above a critical laser intensity). We develop a many-body theory that provides quantitative agreement with the observed location of the transition. The engineered SO coupling-equally applicable for bosons and fermions-sets the stage for the realization of topological insulators in fermionic neutral atom systems.