源于自旋电流涡度的无耗散光伏自旋霍尔效应

中文摘要 AI 辅助

自旋电流涡度（SCV）可产生线性磁自旋霍尔效应[Nature 565, 627 (2019)]，但它在非线性自旋霍尔输运中的作用却鲜有研究。本文表明，在直流电场下，SCV可偏转光激发电子以驱动无耗散光伏自旋霍尔效应（PSHE），其中圆偏振光和线偏振光的光激发分别受贝利曲率和量子度规调控。由于贝利曲率是时间反演对称性（$\boldsymbol{\tau}$）奇宇称，而量子度规是时间反演对称性偶宇称，它们与时间反演对称性奇宇称的SCV的组合分别产生时间反演对称性偶宇称和奇宇称的PSHE。值得注意的是，我们发现时间反演对称性偶宇称PSHE的自旋电流可通过切换光的螺旋度反转，这在单层WTe₂中得到了例证。相比之下，在交替磁体中，时间反演对称性奇宇称PSHE会在奈尔矢量反转时改变符号，这在d波交替磁体模型中得到了验证。除PSHE外，我们还表明SCV偶极子可同时调控近期提出的德鲁德效应和本征非线性自旋霍尔效应。我们的结果揭示了两种可切换的自旋霍尔机制，并确立SCV作为理解无耗散非线性自旋霍尔输运的统一概念。

英文摘要

Spin-current vorticity (SCV) can generate the linear magnetic spin Hall effect [\href{https://doi.org/10.1038/s41586-018-0853-0}{Nature \textbf{565}, 627 (2019)}], yet its role in nonlinear spin Hall transport has been much less explored. Here, we show that, under a dc electric field, SCV can deflect optically excited electrons to drive a dissipationless photovoltaic spin Hall effect (PSHE), in which optical excitation by circularly and linearly polarized light is governed by the Berry curvature and quantum metric, respectively. Because the Berry curvature is $\mathcal{T}$-odd whereas the quantum metric is $\mathcal{T}$-even, their respective combinations with the $\mathcal{T}$-odd SCV give rise to $\mathcal{T}$-even and $\mathcal{T}$-odd PSHEs, where $\mathcal{T}$ denotes time-reversal symmetry. Remarkably, we find that the spin current of the $\mathcal{T}$-even PSHE can be reversed by switching the light helicity, as illustrated in monolayer WTe$_2$. By contrast, the $\mathcal{T}$-odd PSHE in altermagnets changes sign upon Néel-vector reversal, as demonstrated in a $d$-wave altermagnetic model. Beyond the PSHE, we show that the SCV dipole governs both the Drude and intrinsic nonlinear spin Hall effects proposed recently. Our results reveal two switchable spin Hall mechanisms and establish SCV as a unifying concept for understanding dissipationless nonlinear spin Hall transport.

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