Khamehchi M A, Qu Chunlei, Mossman M E, Zhang Chuanwei, Engels P
Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
Nat Commun. 2016 Feb 29;7:10867. doi: 10.1038/ncomms10867.
The quantum emulation of spin-momentum coupling, a crucial ingredient for the emergence of topological phases, is currently drawing considerable interest. In previous quantum gas experiments, typically two atomic hyperfine states were chosen as pseudospins. Here, we report the observation of a spin-momentum coupling achieved by loading a Bose-Einstein condensate into periodically driven optical lattices. The s and p bands of a static lattice, which act as pseudospins, are coupled through an additional moving lattice that induces a momentum-dependent coupling between the two pseudospins, resulting in s-p hybrid Floquet-Bloch bands. We investigate the band structures by measuring the quasimomentum of the Bose-Einstein condensate for different velocities and strengths of the moving lattice, and compare our measurements to theoretical predictions. The realization of spin-momentum coupling with lattice bands as pseudospins paves the way for engineering novel quantum matter using hybrid orbital bands.
自旋-动量耦合的量子模拟是拓扑相出现的关键因素，目前正引起人们的广泛关注。在以往的量子气体实验中，通常选择两个原子超精细态作为赝自旋。在此，我们报告了通过将玻色-爱因斯坦凝聚体加载到周期性驱动的光学晶格中实现自旋-动量耦合的观测结果。静态晶格的s带和p带作为赝自旋，通过一个额外的移动晶格耦合，该移动晶格在两个赝自旋之间诱导出与动量相关的耦合，从而产生s-p混合弗洛凯-布洛赫能带。我们通过测量不同速度和移动晶格强度下玻色-爱因斯坦凝聚体的准动量来研究能带结构，并将我们的测量结果与理论预测进行比较。以晶格能带作为赝自旋实现自旋-动量耦合，为利用混合轨道能带设计新型量子物质铺平了道路。
