光晶格中玻色费米简并混合及极性分子的制备

Polar Molecules have permanent dipoles, the interactions of which appear to be anisotropic. Such interactions are expected to lead to novel quantum phases. In the mean time, because the dipole interactions among molecules can be adjusted by external electronic field, the ultra-cold polar molecules can be loaded to optical lattices to achieve many novel topological quantum models such as artificial gauge-field, Kitaev model and so on. The polar molecules trapped by optical lattices can also be utilized to achieve novel quantum computations. Furthermore, ultra-cold polar molecules can be used to study the chemical reactions dominated by quantum tunneling effects in ultra-cold regime. Due to such advantages the research on polar molecules has attracted a lot of attentions. In this project, based on the setup of a new apparatus, we will start with a quantum degenerate mixture of 23Na and 40K. The mixture will be loaded to a 3D optical lattice to form a Mott insulator with one Na atom and one K atom on each lattice site. By applying a Feshbach resonant field, the hetronuclear Feshbach molecules NaK can be formatted. Further by using Stimulated Raman Adiabatic Passage (STIRAP) scheme, we prepare the polar molecules to the absolute ground state. Due to the significant scientific interests and tremendous potential applications of ultra-cold dipole quantum gas, developing the manipulation techniques of ultra-cold polar molecule and implementing the research is urgent, proactive and of strategic significance.

极性分子具有永久的电偶极矩，其相互作用是各项异性的偶极-偶极相互作用， 会呈现出丰富的奇异量子相变。同时，由于极性分子之间的偶极相互作用可以通过外加电磁场来进行操控，因此可以把超冷极性分子装入光晶格实现格点规范场、Kitaev模型等拓扑量子模型，研究拓扑量子激发， 还可以实现基于极性分子的量子计算等。此外，超冷极性分子可以用来研究极低温下由量子遂穿所主导的化学反应。这一系列的优点使得对极性分子的研究成为当前原子分子操控研究的热点。我们将从超冷Na原子和K原子的简并混合气出发，将其装载到光晶格中形成每个格点上有一个Na原子和一个K原子的Mott绝缘体，通过Feshbach共振技术在每个格点上缔合Feshbach分子，并利用STIRAP相干转换来制备基态极性分子 。鉴于超冷偶极量子气体的重大科学意义和潜在应用价值，发展相关的量子调控技术开展超冷极性分子的研究具有明显的紧迫性、前瞻性和战略性。

实验主要搭建了Na-K超冷玻色费米混合实验装置，包括搭建真空系统，激光系统，水冷系统，时序控制系统等；并在该实验装置基础上完成Na-K玻色费米简并混合气体的制备；Na-K 的Feshbach共振测量和Feshbach分子制备；以及利用Na-K体系中重叠的Feshbach共振完成超冷化学反应观测。首次在实验上直接观测到超低温度下弱束缚分子与自由原子间发生的态态的化学反应，实现了可控态态反应动力学的探测，从而向基于超冷分子的超冷量子化学的研究迈进了重要一步。这一重要研究成果以研究长文的形式发表在国际权威学术期刊《自然•物理学》上[Nature Physics 13, 699-703 (2017)]。