Park Hanbum, Jeong Kwangsik, Maeng InHee, Sim Kyung Ik, Pathak Sachin, Kim Jonghoon, Hong Seok-Bo, Jung Taek Sun, Kang Chul, Kim Jae Hoon, Hong Jongill, Cho Mann-Ho
Department of Physics, Yonsei University, Seoul 03722, Republic of Korea.
Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea.
ACS Appl Mater Interfaces. 2021 May 19;13(19):23153-23160. doi: 10.1021/acsami.1c03168. Epub 2021 May 4.
Owing to their remarkable spin-charge conversion (SCC) efficiency, topological insulators (TIs) are the most attractive candidates for spin-orbit torque generators. The simple method of enhancing SCC efficiency is to reduce the thickness of TI films to minimize the trivial bulk contribution. However, when the thickness reaches the ultrathin regime, the SCC efficiency decreases owing to intersurface hybridization. To overcome these contrary effects, we induced dehybridization of the ultrathin TI film by breaking the inversion symmetry between surfaces. For the TI film grown on an oxygen-deficient transition-metal oxide, the unbonded transition-metal d-orbitals affected only the bottom surface, resulting in asymmetric surface band structures. Spintronic terahertz emission spectroscopy, an emerging tool for investigating the SCC characteristics, revealed that the resulting SCC efficiency in symmetry-broken ultrathin BiSe was enhanced by up to ∼2.4 times.
由于其卓越的自旋-电荷转换（SCC）效率，拓扑绝缘体（TIs）是自旋轨道扭矩发生器最具吸引力的候选材料。提高SCC效率的简单方法是减小TI薄膜的厚度，以最小化平凡的体贡献。然而，当厚度达到超薄范围时，由于表面间杂化，SCC效率会降低。为了克服这些相反的影响，我们通过打破表面之间的反演对称性来诱导超薄TI薄膜的去杂化。对于生长在缺氧过渡金属氧化物上的TI薄膜，未键合的过渡金属d轨道仅影响底面，导致表面能带结构不对称。自旋电子太赫兹发射光谱是一种用于研究SCC特性的新兴工具，它揭示了在对称性破缺的超薄BiSe中产生的SCC效率提高了约2.4倍。
