Spin-orbit coupling in semiconductors

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讲座内容：

Spin-orbit coupling is a key property of semiconductors to explore spintronics without external magnetic field. It can induce spin polarization, acting like an effective magnetic field, in nonmagnetic 3D crystals when the inversion symmetry is broken, as manifested by the bulk Rashba and Dresselhaus effects. We establish that these spin-polarization effects originate fundamentally from specific atomic site asymmetries, rather than, as generally accepted, from the asymmetry of the crystal space group. This understanding leads to the recognition that a previously overlooked hidden form of spin polarization should exist in centrosymmetric crystals. Although all energy bands must be doubly degenerate in centrosymmetric materials, we find that the two components of such doubly degenerate bands could have opposite polarizations, each spatially localized on one of the two separate sectors forming the inversion partners. We demonstrate such hidden spin polarizations in particular centrosymmetric crystals, such as Si and Ge, by first-principles calculations. We also unravel the origin of the Rashba SOC in 3D crystals, which were discovered recently. This new understanding could considerably broaden the range of currently useful spintronic materials and enable the control of spin polarization by means of operations on the atomic scale. I will also present our earlier works on Dresselhuas spin-orbit coupling in 3D bulk, 2D quantum wells, and 1D nanowires. Specifically, we very recently found a rapid transition of the hole Rashba effect from strong field dependence to saturation in semiconductor nanowires. The saturation hole Rashba effect is so strong that even in Si nanowires it reaches about 100 meVA, and is robust against the fluctuations on electric fields and nanowire sizes. This makes Si nanowires a promising avenue for the realization of scalable CMOS-compatible spintronics devices.

主讲人介绍：

骆军委，中国科学院半导体研究所研究员，半导体超晶格国家重点实验室副主任兼计算材料和器件研究组长，中组部青年千人计划获得者。2006年在中国科学院半导体研究所获得博士学位。2007－2014年在美国可再生能源国家实验室工作，先后担任博士后、永久职位科学家、资深科学家。2014年回国工作。研究领域为半导体物理与器件模拟, 在半导体自旋轨道耦合效应、硅基半导体信息功能材料理论设计和发展原子精度全量子力学器件模拟方法等领域开展了系统的研究，已在包括Nature子刊 (5篇)、Phys. Rev. Lett. (6篇)、JACS (1篇)、Nano Lett. (7篇)等国际学术期刊上发表SCIE论文60余篇。多次在APS、ACS和E-MRS等国际重要会议做邀请报告和分会主席。

发布时间：2017-10-30 08:24:38