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中国物理学会期刊

准一维光学晶格超冷原子的自旋霍尔效应

Spin Hall Effect of Ultracold Atoms in a Quasi-One-Dimensional Optical Lattice

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  • 自旋霍尔效应由自旋轨道耦合诱导并展现出自旋流,是凝聚态物理和自旋电子学的重要基石。本文基于准一维光学晶格超冷原子体系,提出了自旋霍尔效应的量子模拟理论方案。在准一维晶格中引入Rashba自旋轨道耦合和线性梯度势,利用含时密度矩阵重整化群方法,计算体系的非平衡动力学演化特别是自旋输运行为。计算结果表明,线性势驱动原子沿晶格方向发生定向输运,而自旋轨道耦合进一步诱导通道间自旋重新分布,出现横向自旋流和横向极化,展现出自旋霍尔效应的典型特征。文章还研究了自旋轨道耦合强度、线性势强度、晶格尺寸以及相互作用强度对自旋霍尔效应的影响。该工作为推动霍尔效应的量子模拟提供了一条可行的超冷原子实现路径,为利用冷原子系统模拟原子输运行为提供了新的理论范式,进一步深化了对人工量子体系中非平衡自旋动力学的理解。

     

    The spin Hall effect is a paradigmatic manifestation of spin-orbit-coupled transverse transport, in which particles with different spin components acquire opposite transverse responses under a longitudinal drive. Ultracold atoms in optical lattices provide a clean and highly controllable platform for exploring such Hall-type dynamics, because the lattice geometry, artificial gauge field, spin-orbit coupling, and interaction strength can be engineered independently. In this work, we propose and numerically analyze a theoretical scheme for simulating spin-Hall-type dynamics with ultracold atoms in a quasi-one-dimensional optical lattice. The system is described by a ladder geometry, where two long-lived orbital states serve as a synthetic dimension. Rashba-type spin-orbit coupling is introduced together with a linear potential gradient along the physical lattice direction. Starting from the ground state without spin-orbit coupling and external driving, we quench on both the Rashba coupling and the linear potential, and calculate the subsequent non-equilibrium dynamics using the time-dependent density matrix renormalization group method. The dynamical response is characterized by the longitudinal particle current, the transverse spin current, and the transverse spin polarization. Our results show that the linear potential drives directional atomic transport along the longitudinal direction, while the Rashba coupling converts this motion into a spin-dependent transverse response. Consequently, opposite transverse currents emerge for the two spin components, giving rise to a finite transverse spin polarization. We further examine how the spin-Hall-type response depends on the Rashba coupling strength, the linear potential gradient, the system size, and the on-site interaction. The transverse spin polarization is enhanced by increasing the spin-orbit coupling and the longitudinal driving strength within the investigated parameter regime, whereas repulsive interactions tend to suppress the transverse response by modifying the local occupation and many-body correlations. These results provide a feasible theoretical route for simulating spin Hall physics in ultracold atomic systems and offer insight into non-equilibrium spin transport in engineered quantum matter.

     

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