Zhao Bing, Karpiak Bogdan, Khokhriakov Dmitrii, Johansson Annika, Hoque Anamul Md, Xu Xiaoguang, Jiang Yong, Mertig Ingrid, Dash Saroj P
Beijing Advanced Innovation Center for Materials Genome Engineering, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, SE-41296, Sweden.
Adv Mater. 2020 Sep;32(38):e2000818. doi: 10.1002/adma.202000818. Epub 2020 Aug 9.
An outstanding feature of topological quantum materials is their novel spin topology in the electronic band structures with an expected large charge-to-spin conversion efficiency. Here, a charge-current-induced spin polarization in the type-II Weyl semimetal candidate WTe and efficient spin injection and detection in a graphene channel up to room temperature are reported. Contrary to the conventional spin Hall and Rashba-Edelstein effects, the measurements indicate an unconventional charge-to-spin conversion in WTe , which is primarily forbidden by the crystal symmetry of the system. Such a large spin polarization can be possible in WTe due to a reduced crystal symmetry combined with its large spin Berry curvature, spin-orbit interaction with a novel spin-texture of the Fermi states. A robust and practical method is demonstrated for electrical creation and detection of such a spin polarization using both charge-to-spin conversion and its inverse phenomenon and utilized it for efficient spin injection and detection in the graphene channel up to room temperature. These findings open opportunities for utilizing topological Weyl materials as nonmagnetic spin sources in all-electrical van der Waals spintronic circuits and for low-power and high-performance nonvolatile spintronic technologies.
拓扑量子材料的一个突出特点是其电子能带结构中新颖的自旋拓扑结构，预计具有较大的电荷到自旋的转换效率。在此，报道了在II型外尔半金属候选材料WTe₂中电荷电流诱导的自旋极化，以及在高达室温的石墨烯通道中高效的自旋注入和检测。与传统的自旋霍尔效应和 Rashba-埃德尔斯坦效应相反，测量结果表明WTe₂中存在一种非常规的电荷到自旋的转换，这在该系统的晶体对称性下原本是被禁止的。由于晶体对称性降低，结合其较大的自旋贝里曲率、与费米态新颖自旋纹理的自旋轨道相互作用，在WTe₂中可能会出现如此大的自旋极化。展示了一种稳健且实用的方法，利用电荷到自旋的转换及其逆现象来电产生和检测这种自旋极化，并将其用于在高达室温的石墨烯通道中进行高效的自旋注入和检测。这些发现为在全电范德华自旋电子电路中利用拓扑外尔材料作为非磁性自旋源，以及用于低功耗和高性能非易失性自旋电子技术开辟了机会。
