Interfacial oxygen-octahedral-tilting-driven electrically tunable topological Hall effect in ultrathin SrRuO₃ films

Topological spin textures as an emerging class of topological matter offer a medium for information storage and processing. The recently discovered topological Hall effect (THE) is considered as a fingerprint for electrically probing the Dzyaloshinskii-Moriya (DM) interaction and corresponding non-trivial spin-textures. In this paper, the THE and its electrical control are observed in ultrathin (8 unit cells. u.c.) 4D ferromagnetic SrRuO₃ films grown on SrTiO₃(0 0 1) substrates, indicating the existence of gate-bias-tunable DM interaction in the single SrRuO₃ layer without contacting 5D oxide SrIrO₃ layer. High-resolution lattice structure analysis revealed that the interfacial RuO₆ octahedral tilting induced by local orthorhombic-to-tetragonal structural phase transition exists across the SrRuO₃/SrTiO₃ interface, which naturally breaks the inversion symmetry. Our theoretical calculations demonstrate that the DM interaction arises owing to the broken inversion symmetry and strong spin-orbit interaction of 4D SrRuO₃. This interfacial RuO₆ octahedral tilting-induced DM interaction can stabilize the Néel-type magnetic skyrmions, which in turn accounts for the observed THE in transport. Besides the fundamental significance, the understanding of THE in oxides and its electrical manipulation presented in this work could advance the low power cost topological electronic and spintronic applications.