Emergence of Topological Hall Effect in a SrRuO Single Layer.

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.