项目名称： 声场作用下ZnO量子点中载流子自旋相干性动力学机理研究

项目编号： No.11504291

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 数理科学和化学

项目作者： 庞华锋

作者单位： 西安科技大学

项目金额： 20万元

中文摘要： 载流子自旋相干性是提高半导体自旋电子器件性能的关键，但如何有效延长自旋弛豫和自旋消相位的动力学机理是制约增强自旋相干性的首要问题，材料结构特性、温度、器件结构和含时外场被认为是重要的影响因素。本申请以非平衡格林函数和哈密顿量对角化方法为基础，结合ZnO量子点的结构特征，建立载流子自旋的全微观自旋动力学Bloch方程数学模型，数值模拟分析出载流子自旋相干性的空时特征与ZnO量子点结构特征、温度和器件结构等之间的关系，从而确定自旋弛豫和自旋消相位的主要机理；考虑压电势控制载流子自旋输运这种新颖方法，进一步建立压电势作用下ZnO量子点中载流子自旋的全微观自旋动力学Bloch方程，计算出自旋弛豫和自旋消相位的特征参量随压电势变化的规律，进而构建出增强ZnO量子点中载流子自旋相干性的动力学新机理，预测压电势作用下在自旋输运与控制过程中产生的新现象、新规律。这为研发新型自旋电子器件提供理论参考。

中文关键词： 自旋相干性；动力学机理；ZnO；量子点；声表面波；压电势

英文摘要： Enhancing carrier spin coherence is very important for improving the performance of semiconductor spintronic devices, which is restricted by the vaguely dynamical mechanisms of the effective increase on the spin relaxation time and spin dephasing time. The structural properties of materials, temperature, device structures, and time-dependent external fields are considered as the crucial factors for the above problems. Based on the nonequilibrium Green's function approach and the diagonalization of effective Hamiltonian, a mathematical model of the fully microscopic kinetic spin Bloch equation is proposed to study the spin dynamics in ZnO quantum dots. The spatial-temporal features of the carrier spin coherence are numerically simulated that are related to structural properties of ZnO quantum dots, temperature, and device structures. The dominated mechanisms of the spin relaxation and spin dephasing are correspondingly discussed and elucidated. Furthermore, a time-dependent piezoelectric potential is used to transport and control the carrier spin as a novel method; and a fully microscopic kinetic spin Bloch equation will be derived for carrier spin dynamics in ZnO quantum dots interacted with the piezoelectric potential. Characteristic parameters of the spin relaxation and spin dephasing are evaluated with the variation of the piezoelectric potential. A novel dynamical mechanism of enhancing carrier spin coherence in ZnO quantum dots is further established, which is used to predict the new spin-related phenomena and laws. This will be very helpful to design and develop novel spintronic devices as a theoretical guidance.

英文关键词： Spin coherence;Dynamical mechanism;ZnO quantum dots;Surface acoustic wave;Piezoelectric potential