近日，西安理工大学的吴亚杰与美国Pinterest公司的Junpeng Hou等人合作，研究了高阶自旋张量霍尔效应中的抵消定理失效与共振自旋张量霍尔电导率。相关研究成果已于2024年12月3日在《物理评论A》上发表。

据悉，随着冷原子模拟量子现象技术的最新进展，人们在具有自旋-张量-动量耦合的更大自旋系统中，发现了高阶自旋张量霍尔效应，这是对著名的大自旋霍尔效应的一种拓展。先前有理论提出，具有Rashba自旋-轨道耦合的二维电子气可以产生无耗散的横向自旋电流，即自旋霍尔效应。

然而，后续研究表明，这种自旋电流会被顶点修正所抵消，这一结论随后被一个不依赖于任何与散射机制、自旋-轨道耦合强度或费米能量相关假设的抵消定理所证实。尽管最近的研究提出了一个普遍存在的内禀自旋-张量霍尔电导率，但目前尚不清楚它是否会像自旋霍尔效应那样消失。

在这项工作中，研究人员解决这一关键问题，并表明通过考虑带间和带内跃迁的贡献，二阶自旋张量电流可以发散，这在某种程度上与量子霍尔效应相似。因此，在有限尺寸的系统中无法观察到普遍的自旋张量霍尔效应。然而，研究人员进一步发现，在磁场作用下，当朗道能级发生交叉时，存在一个可观测的非零自旋张量霍尔电导率共振现象。这项研究揭示了大自旋系统有趣的电导特性，并为实验探索高阶自旋张量霍尔效应及其潜在的器件应用提供了有价值的指导。

附：英文原文

Title: Cancellation-theorem breaking and resonant spin-tensor Hall conductivity in higher-rank spin-tensor Hall effects

Author: Xiaoru He, Ling-Zheng Meng, Junpeng Hou, Xi-Wang Luo, Ya-Jie Wu

Issue&Volume: 2024/12/03

Abstract: With recent advances in simulating quantum phenomena in cold atoms, the higher-rank spin tensor Hall effect was discovered in larger spin systems with spin-tensor-momentum coupling, which is an extension of the celebrated spin Hall effects in larger spins. Previously, it has been proposed that a two-dimensional electron gas with Rashba spin-orbit coupling can generate dissipationless transverse spin current, namely the spin Hall effect. However, later work showed that the spin current is canceled by vertex correction, which was subsequently proven by a cancellation theorem that does not depend on any assumptions related to the scattering mechanism, the strength of spin-orbit coupling, or the Fermi energy. While the recent proposal demonstrates a universal intrinsic spin-tensor Hall conductivity, it is unclear if it vanishes similarly to the spin Hall effect. In this work, we address this critical problem and show that the rank-2 spin-tensor current can be divergent by considering the contributions of both interbranch and intrabranch transitions, which resembles the quantum Hall effect in some sense. So the universal spin-tensor Hall effect cannot be observed in a system with finite size. However, we further show that there is an observable nonzero resonance of spin-tensor Hall conductivity as the Landau levels cross under the magnetic field. Our work reveals interesting conductivity properties of larger-spin systems and will provide valuable guidance for experimental explorations of higher-rank spin-tensor Hall effects, as well as their potential device applications.

DOI: 10.1103/PhysRevA.110.063305

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.063305