利用梯度磁场脉冲产生超冷原子的人工磁场晶格的实验研究

Simulating quantum many body systems with ultracold atomic quantum gas in optical lattices(OLs) is a topical area in modern physics. Spin-dependent OLs with additional internal degrees of freedom can give rise to interesting phenomena, absent in spin-independent OLs. As an active research direction in cold atom physics, artificial gauge fields provide new opportunities to quantum simulation with cold atoms. We propose a general scheme for synthesizing an artificial magnetic lattice (ML) for ultracold atoms using pulsed gradient magnetic fields. The ML lattice constant can overcome the laser wavelength limit in OLs, and is immune to atomic spontaneous emission often encountered in optical lattices. Our scheme can generate spin-dependent OLs and spin-orbit coupling simultaneously, which can give rise to non-trivial bosonic topological ground states in the presence of strong atomic interactions. We will study experimentally the artificial ML synthesized with pulsed gradient magnetic fields, and explore the possible ground states and band structures of ML theoretically. Our proposed research includes: (1) Realizing artificial ML experimentally. (2) Observing the dynamics of atoms in artificial MLs.(3) Studying the ground states and band structures of artificial MLs. Realization of our proposal will expand the repertoire for quantum simulation with ultracold bosonic and fermionic atoms, and provide opportunities for realizing bosonic topological states with cold atoms.

利用光晶格中的原子量子气体模拟量子多体问题是当前物理学的研究热点之一。自旋有关光晶格由于具有额外的内态自由度，可以产生普通光晶格不具有的有趣现象。作为当前冷原子领域最为活跃的方向，人工规范势为冷原子的量子模拟提供了新的思路。本项目提出了利用梯度磁场脉冲合成超冷原子人工磁场晶格的方案，除了可以突破传统光晶格中晶格常数受激光波长的限制，并避免自发辐射引起的原子加热之外，还可同时产生自旋有关晶格和自旋轨道耦合，在引入相互作用后有望产生玻色型的拓扑非平庸基态。本项目将在实验上研究梯度磁场脉冲合成的人工磁场晶格，理论上探索人工磁场晶格的基态和能带性质。具体内容包括：(1)实验实现梯度磁场脉冲合成人工磁场晶格。(2)观察人工磁场晶格中原子的动力学演化。(3)研究人工磁场晶格的基态和能带性质。该方案的实验实现将会拓展基于冷原子的量子模拟实验手段，并为用冷原子实现玻色型拓扑物态提供可能。

基于超冷原子的量子模拟是当前物理学研究的热点之一。本项目提出了利用梯度磁场脉冲合成超冷原子人工磁场晶格的方案，在实验上观察到了一维磁场晶格对原子的衍射，同时我们实验上展示了梯度磁场合成的人工自旋轨道耦合，并利用谐振子势共振增强了人工自旋轨道耦合效应。我们的方案避免了传统拉曼方案中自发辐射引起的加热效应，并且晶格常数或自旋轨道耦合强度连续可调。我们的工作为人工规范势开辟了一条新路径。