自旋轨道耦合诱导的调制不稳定性  

Spin-Orbit-Coupling-Induced Modulation Instability

作　　者：翟云佳 陈园园[1] 张永平 Zhai Yunjia;Chen Yuanyuan;Zhang Yongping(Department of Physics,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学物理系,上海200444

出　　处：《光学学报》2023年第21期17-24,共8页Acta Optica Sinica

基　　金：国家自然科学基金(11974235,11774219)。

摘　　要：原子玻色-爱因斯坦凝聚体的调制稳定性决定了凝聚体的超流属性,是超冷原子物理研究的重要内容。在由拉曼光形成的自旋轨道耦合的玻色-爱因斯坦凝聚体中,存在4种不同的零动量本征态,由于自旋轨道耦合的存在,其中两种态载有流,另两种态不载流。通过对它们进行调制稳定性分析,发现无论在什么参数空间,这4种态都是调制不稳定的,即自旋轨道耦合总是能够诱导出调制不稳定性。这些态的动力学演化揭示调制不稳定性能够产生复杂的图案。Objective Modulation instability is a crucial phenomenon in the study of nonlinear dynamics,where an unstable system results in the destruction of its original states,accompanied by the rapid growth of small perturbation instabilities.The Bose-Einstein condensate serves as an ideal platform for exploring modulation instability due to its precise experimental control over the system's nonlinear dynamics.Therefore,studying modulation instabilities holds profound significance in comprehending the nature of Bose-Einstein condensate systems.In this paper,we reveal that spin-orbit coupling can always introduce modulation instability into a kind of specific state.We call it spin-orbit-coupling-induced modulation instability.The states are specific as they are zero-quasimomentum states.We find that there exist four different zeroquasimomentum states,and we classify them as no-current-carrying states and current-carrying states according to whether the states carry current or not.In literature,modulation instability of the no-current-carrying states has been investigated.The current-carrying states are unique due to their current originating from spin-orbit coupling,and their existence is unstable due to nonlinearity.We find that all these zero-quasimomentum states are modulationally unstable in all parameter regimes.The consequence of such modulation instability is the formation of complex wave structures.Methods The properties of modulation instability and the corresponding nonlinear dynamic images are primarily investigated using Bogoliubov de Gennes(BdG)instability analysis and the split step Fourier method.BdG instability analysis is a widely employed technique for analyzing instability in the study of superfluidity and Bose-Einstein condensates.It primarily examines the system's stability and its response to perturbations by solving nonlinear eigenvalue equations.By diagonalizing the BdG Hamiltonian matrix,the eigenvalues can be obtained.The eigenvalues of the matrix may be complex due to the non-Hermitian nature of

关 键 词：原子与分子物理学 自旋轨道耦合 玻色-爱因斯坦凝聚体 调制不稳定性 

分 类 号：O431.2[机械工程—光学工程]