山西大学Zhaoxin Liang团队研究了自旋相关非线性无Thouless泵浦中矢量孤子的输运。这一研究成果发表在2025年2月27日出版的《物理评论A》杂志上。

在非线性拓扑物理学中，非线性激发的无Thouless泵浦是一个中心话题，通常用标量孤子来说明。矢量孤子具有额外的自旋自由度，由于非线性和拓扑之间的丰富相互作用，表现出标量孤子中没有的现象。

研究组使用Gross-Pitaevskii方程的数值解和拉格朗日变分方法，从理论上研究了约束在自旋相关光学超晶格中的双组分玻色-爱因斯坦凝聚体中矢量孤子的Thouless泵浦。自旋向上和自旋向下分量经历超晶格势，超晶格势位移可调距离????, 导致矢量孤子状态，其分量之间存在相对偏移。研究组证明，作为一个独立的自由度，它为操纵矢量孤子的非线性拓扑相变提供了一种新的控制参数。

具体来说，当????=0时，根据相互作用强度，这两个组件要么被泵送要么被阻止。当固定相互作用强度并改变????时，值得注意的是，研究组发现被捕获的矢量孤子可以重新进入泵浦状态，并表现出量子化的偏移。随着????的持续增加，矢量孤子转变为动态停滞状态；然而，随着????的进一步增加，量化偏移恢复。该工作通过利用不同自旋分量之间的相对运动自由度，为自旋系统中孤子的非线性拓扑泵浦工程开辟了新的途径。

附：英文原文

Title: Transport of vector solitons in spin-dependent nonlinear Thouless pumps

Author: Xuzhen Cao, Chunyu Jia, Hao Lyu, Ying Hu, Zhaoxin Liang

Issue&Volume: 2025/02/27

Abstract: In nonlinear topological physics, Thouless pumping of nonlinear excitations is a central topic, often illustrated by scalar solitons. Vector solitons, with the additional spin degree of freedom, exhibit phenomena absent in scalar solitons due to the enriched interplay between nonlinearity and topology. Here, we theoretically investigate Thouless pumping of vector solitons in a two-component Bose-Einstein condensate confined in spin-dependent optical superlattices, using both numerical solutions of the Gross-Pitaevskii equation and the Lagrangian variational approach. The spin-up and spin-down components experience superlattice potentials that are displaced by a tunable distance dr, leading to a vector soliton state with a relative shift between its components. We demonstrate that dr, as an independent degree of freedom, offers a novel control parameter for manipulating the nonlinear topological phase transition of vector solitons. Specifically, when dr=0, both components are either pumped or arrested, depending on the interaction strength. When fixing the interaction strength and varying dr, remarkably, we find that an arrested vector soliton can reenter the pumped regime and exhibits a quantized shift. As dr continues to increase, the vector soliton transitions into a dynamically arrested state; however, with further increases in dr, the quantized shift revives. Our work paves new routes for engineering nonlinear topological pumping of solitons in spinor systems by utilizing the relative motion degrees of freedom between different spin components.

DOI: 10.1103/PhysRevA.111.023329

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.111.023329