磁性拓扑绝缘体中强烈依赖表面态载流子的自旋轨道转矩
Strongly Surface State Carrier-Dependent Spin-Orbit Torque in Magnetic Topological Insulators.
作者信息
Che Xiaoyu, Pan Quanjun, Vareskic Božo, Zou Jingyi, Pan Lei, Zhang Peng, Yin Gen, Wu Hao, Shao Qiming, Deng Peng, Wang Kang L
机构信息
Department of Electrical and Computer Engineering, Department of Physics and Astronomy and Department of Materials Science and Engineering, University of California, Los Angeles, CA, 90095, USA.
Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, 999077, China.
出版信息
Adv Mater. 2020 Apr;32(16):e1907661. doi: 10.1002/adma.201907661. Epub 2020 Feb 28.
The topological surface states (TSS) in topological insulators (TIs) can exert strong spin-orbit torque (SOT) on adjacent magnetization, offering great potential in implementing energy-efficient magnetic memory devices. However, there are large discrepancies among the reported spin Hall angle values in TIs, and its temperature dependence still remains elusive. Here, the spin Hall angle in a modulation-doped Cr-Bi Sb Te (Cr-BST) film is quantitatively determined via both transport and optic approaches, where consistent results are obtained. A large spin Hall angle of ≈90 in the modulation-doped Cr-BST film is demonstrated at 2.5 K, and the spin Hall angle drastically decreases to 0.3-0.5 as the temperature increases. Moreover, by tuning the top TSS carrier concentration, a competition between the top and bottom TSS in contributing to SOT is observed. The above phenomena can account for the large discrepancies among the previously reported spin Hall angle values and reveal the unique role of TSS in generating SOT.
拓扑绝缘体（TI）中的拓扑表面态（TSS）能够对相邻的磁化强度施加强大的自旋轨道转矩（SOT），这在实现节能磁存储器件方面具有巨大潜力。然而，TI中报道的自旋霍尔角值之间存在很大差异，其温度依赖性仍然难以捉摸。在此，通过输运和光学方法定量测定了调制掺杂的Cr-Bi Sb Te（Cr-BST）薄膜中的自旋霍尔角，得到了一致的结果。在2.5K时，调制掺杂的Cr-BST薄膜表现出约90的大自旋霍尔角，随着温度升高，自旋霍尔角急剧降至0.3 - 0.5。此外，通过调节顶部TSS载流子浓度，观察到顶部和底部TSS在贡献SOT方面的竞争。上述现象可以解释先前报道的自旋霍尔角值之间的巨大差异，并揭示TSS在产生SOT中的独特作用。
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