Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy
Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy
复制标题
DOI：
10.1103/physrevb.53.8105
复制
发表时间：
1996-03-15
影响因子：
3.7
通讯作者：
vanKempen, H
中科院分区：
文献类型：
--
作者：
Prins, MWJ;Jansen, R;vanKempen, H
我们描述了一个借助光自旋取向进行自旋极化隧穿的模型以及相关实验。这涉及磁性材料和砷化镓（GaAs）之间的隧道结，其中后者用圆偏振光进行光激发以产生自旋极化载流子。我们提出了一个输运模型，该模型考虑了半导体表面态中的载流子俘获，并根据与自旋相关的能量分布函数来描述半导体表面。所谓的表面自旋分裂可以通过半导体次表面区域中极化电子和空穴流的平衡、磁性材料和半导体表面之间穿过隧道势垒的极化隧穿电流以及半导体表面的自旋弛豫来计算。我们展示了在环境条件下，用GaAs针尖和Pt/Co多层样品在扫描隧道显微镜中获得的实验数据。发现隧道电流存在螺旋度不对称性（即与圆偏振相关的隧道电流），其大小为4皮安，并且证实这不是由于光功率的变化引起的。根据我们的模型和估算，这一观测结果可以用自旋极化隧穿来解释，半导体表面自旋分裂和自旋寿命的下限分别为4毫伏和0.4纳秒。
We describe a model as well as experiments on spin-polarized tunneling with the aid of optical spin orientation. This involves tunnel junctions between a magnetic material and gallium arsenide (GaAs), where the latter is optically excited with circularly polarized light in order to generate spin-polarized carriers. We present a transport model that takes account of carrier capture in the semiconductor surface states, and describes the semiconductor surface in terms of a spin-dependent energy distribution function. The so-called surface spin splitting can be calculated from the balance of the polarized electron and hole flow in the semiconductor subsurface region, the polarized tunneling current across the tunnel barrier between the magnetic material and the semiconductor surface, and the spin relaxation at the semiconductor surface. We present experimental data obtained in a scanning tunneling microscope with a GaAs tip and a Pt/Co multilayer sample under ambient conditions. A helicity asymmetry of tunnel current (i.e., a circular-polarization-dependent tunnel current) was found with a magnitude of 4 pA, which was verified not to be due to variations of the optical power. According to our model and estimations, this observation can be explained by spin-polarized tunneling, with a lower limit to the semiconductor surface spin splitting and spin lifetime of 4 mV and 0.4 ns, respectively.