三维自旋轨道耦合玻色气体中对称性保护的Skyrmions
Symmetry protected skyrmions in 3D spin-orbit coupled Bose gases
摘要：
本文研究了$1/2$型赝自旋玻色气体在三维弱自旋轨道耦合简谐势阱中的变分问题。这种自旋轨道耦合混合了具有不同宇称的态，这启发我们用总角动量的本征态来近似单粒子态，即简谐$s$波态和$p$波态的叠加。由于时间反演对称性受到两体相互作用的保护，我们将变分序参量设置为两个相互时间反演对称的总角动量本征态的组合。变分结果基本上再现了最近由Kawakami { \it et al.}确定的3D Skyrmion类基态。我们发现，这些skyrmion在这个模型中出现的基态主要是由$p$波空间模式涉及的变化序参量，驱动两个自旋组件空间分离。我们发现该系统的基态根据种内和种间相互作用的相对大小分为两个具有不同密度分布对称性的相：相I具有宇称对称和轴对称的密度分布，而相II具有离散旋转和时间反演对称的特殊联合对称性。随着相互作用强度的增加，相变发生在具有不同密度分布的两相之间，而拓扑3D Skyrmion状自旋织构是对称性保护的。
英文摘要：
We present a variational study of pseudo-spin $1/2$ Bose gases in a harmonic trap with weak 3D spin-orbit coupling of $\bmsigma\cdot\mathbf{p}$ type. This spin-orbit coupling mixes states with different parities, which inspires us to approximate the single particle state with the eigenstates of the total angular momentum, i.e. superposition of harmonic $s$-wave and $p$-wave states. As the time reversal symmetry is protected by two-body interaction, we set the variational order parameter as the combination of two mutually time reversal symmetric eigenstates of the total angular momentum. The variational results essentially reproduce the 3D skyrmion-like ground state recently identified by Kawakami {\it et al.}. We show that these skyrmion-like ground states emerging in this model are primarily caused by $p$ wave spatial mode involving in the variational order parameter that drives two spin components spatially separated. We find the ground state of this system falls into two phases with different density distribution symmetries depending on the relative magnitude of intraspecies and interspecies interaction: Phase I has parity symmetric and axisymmetric density distributions, while Phase II is featured with special joint symmetries of discrete rotational and time reversal symmetry. With the increasing interaction strength the transition occurs between two phases with distinct density distributions, while the topological 3D skyrmion-like spin texture is symmetry protected.
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。
