超冷87Rb原子在二维光晶格中Mott绝缘态的实验实现  

Experimental realization of Mott insulator of ultracold 87Rb atoms in two-dimensional optical lattice

作　　者：文凯 王良伟 周方 陈良超[1,2] 王鹏军 孟增明[1,2] 张靖 Wen Kai;Wang Liang-Wei;Zhou Fang;Chen Liang-Chao;Wang Peng-Jun;Meng Zeng-Ming;Zhang Jing(State Key Laboratory of Quantum Optics and Quantum Optics Devices,Institute of Opto-Electronics,Shanxi University,Taiyuan 030006,China;Collaborative Innovation Center of Extreme Optics,Shanxi University,Taiyuan 030006,China)

机构地区：[1]山西大学光电研究所,量子光学与光量子器件国家重点实验室,太原030006 [2]山西大学极端光学协同创新中心,太原030006

出　　处：《物理学报》2020年第19期74-80,共7页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2016YFA0301602,2018YFA0307600);国家自然科学基金(批准号:11804203,11904217)资助的课题.

摘　　要：超冷原子气体的量子相变是研究量子关联多体物理的核心内容之一.本文采用单一激光光束通过折叠反射产生二维光晶格,通过控制激光偏振产生两种不同的二维光晶格结构,一种是两个独立的一维光晶格构成,另一种是两个方向的一维光晶格互相干涉形成.将超冷87Rb原子装载到二维光晶格中,通过改变光晶格激光功率调控原子在光晶格中的隧穿强度和相互作用强度,观察到87Rb原子从超流态到Mott绝缘态之间的量子相变,并且分析了两种光晶格对量子相变的影响,为今后开展光晶格中强关联物理研究奠定基础.Quantum phase transition of ultracold atomic gas is one of the core contents in the study of quantum correlational many-body systems.In this paper,two-dimensional(2D)optical lattices are generated by a single fold retroreflected laser beam,and this scheme is used to experimentally design and implement the 2D optical lattice of double wells suitable for isolating and manipulating an array of individual pairs of atoms and predict a topological semimetal in the high orbital bands in this 2D lattice.Two types of optical lattice structures are produced by controlling the laser polarization.One type is the usual 2D optical lattice,which is formed by two independent one-dimensional(1D)optical lattices in two directions and named in-plane lattice,and the other type is the lattice that is formed by the interference between two one-dimensional optical lattices in two directions and called out-plane lattice.When 87Rb BEC(Bose-Einstein condensation)is loaded into the 2D optical lattice,the quantum phase transition between superfluid state and Mott insulator state is observed by controlling the tunneling and in-site interaction.And the phase transition from superfluid state to Mott insulator is judged by observing whether there are interferential lattice points in momentum space.The lattice depths of two cases can be calibrated by Kapitza-Dirac scattering in the ultracold atomic experiment through the time-of-flight absorption imaging.In the in-plane optical lattice,some incorrect points appear in the 45°direction,because the linear polarization degree of beam is impure after being reflected by mirrors and two direction of beam are not completely orthogonal to each other.It is obvious that the two cases have different phase transition points,which is due mainly to the difference in structure.For the in-plane lattice,there are two independent 1D optical lattices,and for the out-plane lattice,the two direction beams mutually interfere with each other,therefore,two optical lattices are not independent of each other.The atoms co

关 键 词：光晶格 量子相变 量子关联多体物理 超流 MOTT 绝缘态 

分 类 号：O469[理学—凝聚态物理]