Electron-nuclear spin dynamics of Ga2+ paramagnetic centers probed by spin-dependent recombination: A master equation approach
Electron-nuclear spin dynamics of Ga2+ paramagnetic centers probed by spin-dependent recombination: A master equation approach
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DOI：
10.1103/physrevb.95.195204
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发表时间：
2017-05-10
影响因子：
3.7
通讯作者：
Kunold, A.
中科院分区：
文献类型：
--
作者：
Ibarra-Sierra, V. G.;Sandoval-Santana, J. C.;Kunold, A.
与金刚石中的氮空位中心和硅中的杂质原子类似，砷化镓中的间隙镓深顺磁中心已被证明对自旋电子器件的发展具有有用的特性。在其他有趣的特性中，在圆偏振光下，镓中心充当自旋过滤器，动态地极化自由和束缚电子，达到创纪录的自旋极化（接近100%）。此外，最近对法拉第组态磁场下自旋滤波效应放大的观察表明，结合电子和原子核的超精细相互作用允许对核自旋极化进行光学操纵。尽管在镓中心的核自旋极化机制已经被很好地理解，但核自旋弛豫的起源和类似奥弗豪斯磁场的形成仍然是难以捉摸的。在这项工作中，我们建立了一个基于主方程方法的模型来描述镓中心与自由电子和空穴相互作用的电子和核自旋极化的演变。我们的结果与已有的实验观察结果很好地吻合。特别是，我们能够在法拉第组态磁场的圆极化激励下再现自旋滤波效应的放大。关于核自旋弛豫，讨论了核偶极和四极相互作用的作用。我们的研究结果表明，除了超精细相互作用外，自旋弛豫机制是理解自旋过滤效应放大和类奥弗豪斯磁场出现的关键。为了更深入地了解超精细相互作用和弛豫机制的相互作用，我们还进行了脉冲激发体制下的计算。我们的模型结果允许我们提出一个基于时间分辨光谱的实验方案。它由一个泵浦-探针光致发光方案组成，通过光致发光测量来检测和跟踪电子-核的触发器。
Similar to nitrogen-vacancy centers in diamond and impurity atoms in silicon, interstitial gallium deep paramagnetic centers in GaAsN have been proven to have useful characteristics for the development of spintronic devices. Among other interesting properties, under circularly polarized light, gallium centers act as spin filters that dynamically polarize free and bound electrons reaching record spin polarizations (close to 100%). Furthermore, the recent observation of the amplification of the spin filtering effect under a Faraday configuration magnetic field has suggested that the hyperfine interaction that couples bound electrons and nuclei permits the optical manipulation of the nuclear spin polarization. Even though the mechanisms behind the nuclear spin polarization in gallium centers are fairly well understood, the origin of nuclear spin relaxation and the formation of an Overhauser-like magnetic field remain elusive. In this work we develop a model based on the master equation approach to describe the evolution of electronic and nuclear spin polarizations of gallium centers interacting with free electrons and holes. Our results are in good agreement with existing experimental observations. In particular, we are able to reproduce the amplification of the spin filtering effect under a circularly polarized excitation in a Faraday configuration magnetic field. In regard to the nuclear spin relaxation, the roles of nuclear dipolar and quadrupolar interactions are discussed. Our findings show that, besides the hyperfine interaction, the spin relaxation mechanisms are key to understand the amplification of the spin filtering effect and the appearance of the Overhauser-like magnetic field. To gain a deeper insight in the interplay of the hyperfine interaction and the relaxation mechanisms, we have also performed calculations in the pulsed excitation regime. Our model's results allow us to propose an experimental protocol based on time-resolved spectroscopy. It consists of a pump-probe photoluminescence scheme with the detection and the tracing of the electron-nucleus flip-flops through photoluminescence measurements.