Milletarì Mirco, Offidani Manuel, Ferreira Aires, Raimondi Roberto
Dipartimento di Matematica e Fisica, Università Roma Tre, 00146 Rome, Italy and Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), Singapore 138671, Singapore.
Department of Physics, University of York, York YO10 5DD, United Kingdom.
Phys Rev Lett. 2017 Dec 15;119(24):246801. doi: 10.1103/PhysRevLett.119.246801. Epub 2017 Dec 14.
We present a theoretical analysis of two-dimensional Dirac-Rashba systems in the presence of disorder and external perturbations. We unveil a set of exact symmetry relations (Ward identities) that impose strong constraints on the spin dynamics of Dirac fermions subject to proximity-induced interactions. This allows us to demonstrate that an arbitrary dilute concentration of scalar impurities results in the total suppression of nonequilibrium spin Hall currents when only Rashba spin-orbit coupling is present. Remarkably, a finite spin Hall conductivity is restored when the minimal Dirac-Rashba model is supplemented with a spin-valley interaction. The Ward identities provide a systematic way to predict the emergence of the spin Hall effect in a wider class of Dirac-Rashba systems of experimental relevance and represent an important benchmark for testing the validity of numerical methodologies.
我们对存在无序和外部微扰情况下的二维狄拉克 - 拉什巴系统进行了理论分析。我们揭示了一组精确的对称关系（沃德恒等式），这些关系对受近邻诱导相互作用影响的狄拉克费米子的自旋动力学施加了强约束。这使我们能够证明，当仅存在拉什巴自旋 - 轨道耦合时，任意稀释浓度的标量杂质会导致非平衡自旋霍尔电流完全被抑制。值得注意的是，当最小狄拉克 - 拉什巴模型补充了自旋 - 谷相互作用时，有限的自旋霍尔电导率得以恢复。沃德恒等式为预测更广泛一类具有实验相关性的狄拉克 - 拉什巴系统中自旋霍尔效应的出现提供了一种系统方法，并且是检验数值方法有效性的重要基准。
