Covariant conservation laws and the spin Hall effect in Dirac-Rashba systems

• Published in: arXiv.org
• Main Authors: Milletari, Mirco, Offidani, Manuel, Ferreira, Aires, Raimondi, Roberto
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 20.12.2017
• Subjects: Conservation laws; Electromagnetism; Fermions; Hall effect; Physics - Mesoscale and Nanoscale Physics; Spin dynamics; Spin-orbit interactions; Two dimensional analysis
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1705.08898

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.