Ab initio ultrafast spin dynamics in solids
Ab initio ultrafast spin dynamics in solids
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DOI：
10.1103/physrevb.104.184418
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发表时间：
2020-12
影响因子：
3.7
通讯作者：
Junqing Xu;A. Habib;R. Sundararaman;Y. Ping
中科院分区：
文献类型：
--
作者：
Junqing Xu;A. Habib;R. Sundararaman;Y. Ping
自旋弛豫和退相干是自旋电子学和基于自旋的量子信息科学的核心。目前，没有一种理论方法可以准确地预测固体的自旋弛豫，包括必要的散射路径，所需的模拟时间为ns到ms。我们提出了一种基于Lindblad动力学的第一性原理实时密度矩阵方法来模拟一般固态系统的超快自旋动力学，包括各种散射过程。通过对电子-声子、电子-杂质和电子-电子散射等泵浦、探针和散射过程的完整理论描述，我们的方法可以直接模拟任意温度和掺杂水平下泵浦-探针耦合自旋和电子动力学的超快测量。将该方法应用于GaAs原型系统，结果与实验结果吻合良好。我们发现不同的散射机制和声子模式的相对贡献在自旋和载流子弛豫过程之间有很大的不同。重要的是，与以往基于模型哈密顿量的工作形成鲜明对比的是，我们指出在低温下电子-电子散射对自旋弛豫非常重要。最重要的是，我们研究了常用的现象学D‘yakonov- perel ’关系的适用条件，该关系可能在个别散射过程中失效。我们的工作为固体中的自旋弛豫提供了一个预测计算平台，这对于设计自旋电子学和量子信息技术的理想新材料具有前所未有的潜力。
Spin relaxation and decoherence is at the heart of spintronics and spin-based quantum information science. Currently, no theoretical approaches can accurately predict spin relaxation of solids including necessary scattering pathways for required ns to ms simulation time. We present a first-principles real-time density-matrix approach based on Lindblad dynamics to simulate ultrafast spin dynamics including various scattering processes for general solid-state systems. Through the complete theoretical descriptions of pump, probe and scattering processes including electron-phonon, electron-impurity and electron-electron scatterings, our method can directly simulate the ultrafast pump-probe measurements for coupled spin and electron dynamics at any temperatures and doping levels. We apply this method to a prototypical system GaAs and obtain excellent agreement with experiments. We found that the relative contributions of different scattering mechanisms and phonon modes vary considerably between spin and carrier relaxation processes. Importantly, in sharp contrast to previous work based on model Hamiltonians, we point out that at low temperatures the electron-electron scattering becomes very important for spin relaxation. Most importantly, we examine the applicable conditions of the commonly-used phenomenological D'yakonov-Perel' relation, which may break down for individual scattering processes. Our work provides a predictive computational platform for spin relaxation in solids, which has unprecedented potentials for designing new materials ideal for spintronics and quantum information technology.