Microscopic Linear Response Theory of Spin Relaxation and Relativistic Transport Phenomena in Graphene
Microscopic Linear Response Theory of Spin Relaxation and Relativistic Transport Phenomena in Graphene
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DOI：
10.3390/condmat3020018
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发表时间：
2018-04
期刊：
影响因子：
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通讯作者：
Manuel Offidani;R. Raimondi;Aires Ferreira
中科院分区：
文献类型：
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作者：
Manuel Offidani;R. Raimondi;Aires Ferreira
我们提出了一个统一的理论框架，用于研究具有赝自旋-自旋耦合的无序二维狄拉克系统中的自旋动力学和相对论输运现象。该形式主义应用于具有均匀 Bychkov-Rashba 相互作用的石墨烯的典型案例，并被证明可以捕获自旋弛豫过程和相关的电荷到自旋互变现象，以响应一般的外部扰动，包括自旋密度波动和电场。对弱自旋轨道相互作用的扩散范围内的广义自旋磁化率的受控图解评估使我们能够证明自旋和动量寿命满足弱（高斯）和共振（酉）非磁无序的标准 Dyakonov-Perel 关系。最后，我们证明了通过利用自旋可观测量的 SU(2) 协变守恒定律可以在零频率极限下导出自旋弛豫率。我们的结果为自旋弛豫的完全量子力学描述奠定了基础，在具有弱自旋轨道场的原始石墨烯样品和具有增强自旋轨道效应的石墨烯异质结构中，目前引起了广泛关注。
We present a unified theoretical framework for the study of spin dynamics and relativistic transport phenomena in disordered two-dimensional Dirac systems with pseudospin-spin coupling. The formalism is applied to the paradigmatic case of graphene with uniform Bychkov-Rashba interaction and shown to capture spin relaxation processes and associated charge-to-spin interconversion phenomena in response to generic external perturbations, including spin density fluctuations and electric fields. A controlled diagrammatic evaluation of the generalized spin susceptibility in the diffusive regime of weak spin-orbit interaction allows us to show that the spin and momentum lifetimes satisfy the standard Dyakonov-Perel relation for both weak (Gaussian) and resonant (unitary) nonmagnetic disorder. Finally, we demonstrate that the spin relaxation rate can be derived in the zero-frequency limit by exploiting the SU(2) covariant conservation laws for the spin observables. Our results set the stage for a fully quantum-mechanical description of spin relaxation in both pristine graphene samples with weak spin-orbit fields and in graphene heterostructures with enhanced spin-orbital effects currently attracting much attention.