Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Spintronics Research Group (PROSPIN), POBox 91, H-1521, Budapest, Hungary.
Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, POBox 49, H-1525, Budapest, Hungary.
Sci Rep. 2017 Aug 30;7(1):9949. doi: 10.1038/s41598-017-09759-0.
We study the spin-relaxation time in materials where a large spin-orbit coupling (SOC) is present which breaks the spatial inversion symmetry. Such a spin-orbit coupling is realized in zincblende structures and heterostructures with a transversal electric field and the spin relaxation is usually described by the so-called D'yakonov-Perel' (DP) mechanism. We combine a Monte Carlo method and diagrammatic calculation based approaches in our study; the former tracks the time evolution of electron spins in a quasiparticle dynamics simulation in the presence of the built-in spin-orbit magnetic fields and the latter builds on the spin-diffusion propagator by Burkov and Balents. Remarkably, we find a parameter free quantitative agreement between the two approaches and it also returns the conventional result of the DP mechanism in the appropriate limit. We discuss the full phase space of spin relaxation as a function of SOC strength, its distribution, and the magnitude of the momentum relaxation rate. This allows us to identify two novel spin-relaxation regimes; where spin relaxation is strongly non-exponential and the spin relaxation equals the momentum relaxation. A compelling analogy between the spin-relaxation theory and the NMR motional narrowing is highlighted.
我们研究了在存在大自旋轨道耦合（SOC）的材料中的自旋弛豫时间，这种 SOC 破坏了空间反演对称性。这种自旋轨道耦合存在于锌矿结构和具有横向电场的异质结构中，自旋弛豫通常由所谓的 D'yakonov-Perel'（DP）机制来描述。我们在研究中结合了蒙特卡罗方法和基于图论的计算方法；前者在存在内置自旋轨道磁场的准粒子动力学模拟中跟踪电子自旋的时间演化，后者基于 Burkov 和 Balents 的自旋扩散传播子。值得注意的是，我们发现这两种方法之间存在无参数的定量一致性，并且在适当的极限下也返回了 DP 机制的传统结果。我们讨论了自旋弛豫作为 SOC 强度、分布和动量弛豫率的函数的全相空间。这使我们能够识别两种新的自旋弛豫状态；其中自旋弛豫强烈非指数，并且自旋弛豫等于动量弛豫。突出强调了自旋弛豫理论和 NMR 运动变窄之间的引人入胜的类比。
