人工自旋轨道耦合玻色-爱因斯坦凝聚体的元激发
Elementary Excitations in A Synthetic Spin-Orbit-Coupled Bose-Einstein Condensate

文章研究了准一维人工自旋轨道耦合玻色-爱因斯坦凝聚体中的元激发. 利用平均场理论和波戈留波夫近似方法，分别计算了此原子凝聚体在依赖于拉曼耦合强度的零动量相和平面波相的激发谱. 结果表明，在零动量相时体系激发谱的2个分支都呈现出对称结构；相反地，在较小拉曼耦合强度时的平面波相，激发谱呈现出旋子最低结构，从而预示了体系从平面波相到条纹相的相变. 文中证明了在平面波相和零动量相的相变附近，低频元激发的声速急剧下降并消失于相变点. 文章全面分析了人工自旋轨道耦合原子凝聚体的元激发特性，为实验研究该类崭新的多体系统提供理论支持.
： 〖JP2〗The elementary excitations in a quasi-one-dimensional synthetic spin-orbit-coupled Bose-Einstein condensate are investigated in this paper. With the mean-field approximation and the Bogoliubov approach, the excitation spectrum of the atomic condensate in the zero-momentum and plane-wave phases is calculated, respectively, which depend on the Raman coupling strength. It is shown that the two branches of the excitation spectrum in zero-momentum phase both exhibit symmetry structure. In contrast, the excitation spectrum〖JP〗 exhibits roton minimum structure in the plane-wave phase for small Raman coupling strength, which provides the onset of the phase transition to the stripe phase. It is also shown that the sound speed of the low-frequency excitations decreases sharply and vanishes near the phase transition between the plane-wave and zero-momentum phases. This work gives comprehensive analysis of novel properties of elementary excitations in a synthetic spin-orbit-coupled atomic condensate, which may provide theoretical support for experimental studies on this new kind of many-body system