arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2108.13784cond-mat.quant-gas
收藏

自旋-轨道耦合玻色-爱因斯坦凝聚体中相互作用诱导的拓扑Bogoliubov激发

Interaction induced topological Bogoliubov excitations in a spin-orbit coupled Bose-Einstein condensate

Guan-Hua Huang, Guang-Quan Luo, Zhigang Wu, Zhi-Fang Xu

摘要:

本文研究了二维正方形光晶格中弱相互作用、自旋-轨道耦合的玻色-爱因斯坦凝聚体的拓扑非平凡激发。Sun等人,物理修订版信函121,150401(2018)]。我们专注于系统不受塞曼场的情况下,因此不表现出非平凡的单粒子带拓扑。特别感兴趣的是粒子相互作用的作用,以及它的相互作用与系统的对称性在生产拓扑非平凡的激发。我们发现非相互作用系统具有丰富的对称性,包括$\mathcal{PT}$对称性,修正的二面角点群对称性$\tilde D_4$和非对称对称性.这些对称性的结合保证了单粒子能带在布里渊区边缘存在着一对简并的狄拉克点。在存在粒子相互作用和足够的自旋轨道耦合的情况下,原子凝聚在具有净磁化的基态,这自发地破坏了$\mathcal{PT}$和$\tilde D_4$对称性。我们证明,这种对称性破缺导致的Bogoliubov频谱和相应的拓扑非平凡的激发在狄拉克点的间隙开放。我们确认的非平凡的拓扑结构,通过计算的最低激发带的陈数,并表明,无间隙的边缘状态的形式,其特征在于由不同的值的陈数的系统的接口。

英文摘要:

We study topologically non-trivial excitations of a weakly interacting, spin-orbit coupled Bose-Einstein condensate in a two-dimensional square optical lattice, a system recently realized in experiment [W. Sun et al., Phys. Rev. Lett. 121, 150401 (2018)]. We focus on situations where the system is not subjected to a Zeeman field and thus does not exhibit nontrivial single-particle band topology. Of special interest then is the role of particle interaction as well as its interplay with the symmetry properties of the system in producing topologically non-trivial excitations. We find that the non-interacting system possesses a rich set of symmetries, including the $\mathcal{PT}$ symmetry, the modified dihedral point group symmetry $\tilde D_4$ and the nonsymmorphic symmetry. These combined symmetries ensure the existence of pairs of degenerate Dirac points at the edge of Brillouin zone for the single-particle energy bands. In the presence of particle interaction and with sufficient spin-orbit coupling, the atoms condense in a ground state with net magnetization which spontaneously breaks the $\mathcal{PT}$ and $\tilde D_4$ symmetry. We demonstrate that this symmetry breaking leads to a gap opening at the Dirac point for the Bogoliubov spectrum and consequentially topologically non-trivial excitations. We confirm the non-trivial topology by calculating the Chern numbers of the lowest excitation bands and show that gapless edge states form at the interface of systems characterized by different values of the Chern number.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑