Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore.
NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore.
Adv Mater. 2019 Feb;31(8):e1807008. doi: 10.1002/adma.201807008. Epub 2019 Jan 7.
Topological Hall effect (THE), appearing as bumps and/or dips in the Hall resistance curves, is considered as a hallmark of the skyrmion spin texture originated from the inversion symmetry breaking and spin-orbit interaction. Recently, Néel-type skyrmion is proposed based on the observed THE in 5d transition metal oxides heterostructures such as SrRuO /SrIrO bilayers, where the interfacial Dzyaloshinskii-Moriya interaction (DMI), due to the strong spin-orbit coupling (SOC) in SrIrO and the broken inversion symmetry at the interface, is believed to play a significant role. Here the emergence of THE in SrRuO single layers with thickness ranging from 3 to 6 nm is experimentally demonstrated. It is found that the oxygen octahedron rotation in SrRuO also has a significant effect on the observed THE. Furthermore, the THE may be continuously tuned by an applied electrical field. It is proposed that the large SOC of Ru ions together with the broken inversion symmetry, mainly from the interface, produce the DMI that is responsible for the observed THE. The emergence of the gate-tunable DMI in SrRuO single layer may stimulate further investigations of new spin-orbit physics in strong SOC oxides.
拓扑霍尔效应（THE）表现为 Hall 电阻曲线中的凸起和/或凹陷，被认为是由反演对称性破缺和自旋轨道相互作用引起的斯格明子自旋织构的标志。最近，在 SrRuO/SrIrO 双层等 5d 过渡金属氧化物异质结构中观察到的 THE 提出了奈尔型斯格明子，其中由于 SrIrO 中的强自旋轨道耦合（SOC）和界面处的反演对称性破缺，界面上的 Dzyaloshinskii-Moriya 相互作用（DMI）被认为起着重要作用。在这里，实验证明了厚度在 3 到 6nm 之间的 SrRuO 单层中存在 THE。结果发现，SrRuO 中氧八面体的旋转对观察到的 THE 也有显著影响。此外，通过施加电场可以连续调节 THE。提出 Ru 离子的大 SOC 以及主要来自界面的反演对称性破缺产生了导致观察到的 THE 的 DMI。SrRuO 单层中门可调 DMI 的出现可能会激发对强 SOC 氧化物中新型自旋轨道物理的进一步研究。
