中心自旋问题中核自旋动力学的自猝灭
Self-Quenching of Nuclear Spin Dynamics in Central Spin Problem
摘要：
在中心自旋$s=1/2$模型的框架下，研究了双量子点中两电子与核自旋的超精细相互作用和自旋轨道耦合的驱动动力学。核子系统的动态演变响应于朗道-齐纳单重态-三重态跃迁的电子子系统控制的外部栅极电压。如果没有噪声和自旋轨道耦合，随后的朗道-齐纳跃迁在大约$10^4$扫描后消失，系统自猝灭，核自旋达到众多玻璃暗态之一。我们提出了一个分析模型，捕捉这种现象。我们还占的多核物种的内容的点和数值确定周围$10^7$核自旋的演变在高达$2\times10^5$朗道-齐纳转换。在没有自旋轨道耦合的情况下，自猝灭是鲁棒的，并且在任意比率的核自旋进动时间和朗道-齐纳扫描之间的等待时间以及在中等噪声下设置。在存在中等量级的自旋轨道耦合时，当等待时间与其中一个核素的进动时间共振时，核极化的动力学演化导致自旋轨道耦合的频闪屏蔽。然而，共振或强自旋轨道耦合的小偏差破坏了这种屏蔽。我们认为，成功的反馈回路技术建立核梯度是基于自旋轨道耦合的效果。
英文摘要：
We consider, in the framework of the central spin $s=1/2$ model, driven dynamics of two electrons in a double quantum dot subject to hyperfine interaction with nuclear spins and spin-orbit coupling. The nuclear subsystem dynamically evolves in response to Landau-Zener singlet-triplet transitions of the electronic subsystem controlled by external gate voltages. Without noise and spin-orbit coupling, subsequent Landau-Zener transitions die out after about $10^4$ sweeps, the system self-quenches, and nuclear spins reach one of the numerous glassy dark states. We present an analytical model that captures this phenomenon. We also account for the multi-nuclear-specie content of the dots and numerically determine the evolution of around $10^7$ nuclear spins in up to $2\times10^5$ Landau-Zener transitions. Without spin-orbit coupling, self-quenching is robust and sets in for arbitrary ratios of the nuclear spin precession times and the waiting time between Landau-Zener sweeps as well as under moderate noise. In presence of spin-orbit coupling of a moderate magnitude, and when the waiting time is in resonance with the precession time of one of the nuclear species, the dynamical evolution of nuclear polarization results in stroboscopic screening of spin-orbit coupling. However, small deviations from the resonance or strong spin-orbit coupling destroy this screening. We suggest that the success of the feedback loop technique for building nuclear gradients is based on the effect of spin-orbit coupling.
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