Manipulating Momentum-Space and Real-Space Topological States in Metallic Strontium Ruthenate Ultrathin Films

TL;DR

This study demonstrates the existence of topological states, including skyrmions, in ultrathin SrRuO3 films through experimental measurements and band structure analysis, overcoming previous challenges related to their detection.

Contribution

It provides direct evidence of skyrmions and topological states in ultrathin SrRuO3 films, using advanced heterostructure fabrication and ARPES measurements.

Findings

Ultrathin SrRuO3 remains metallic down to monolayer.

Anomalous Hall effect persists across various thicknesses.

Skyrmions are evidenced in ultrathin SrRuO3.

Abstract

SrRuO3, a 4d transition metal oxide, has gained significant interest due to its topological states in both momentum space (Weyl points) and real space (skyrmions). However, probing topological states in ultrathin SrRuO3 faces challenges such as the metal-insulator transition and questioned existence of skyrmions due to possible superposition of opposite anomalous Hall effect (AHE) signals. To address these issues, we investigate ultrathin SrRuO3/SrIrO3 heterostructures and their AHE and topological Hall effect (THE). Our results reveal metallized ultrathin SrRuO3 down to the monolayer limit with an AHE signal. ARPES measurements confirm the metallic and topological band structure of ultrathin SrRuO3. Furthermore, the AHE sign remains negative over a wide thickness range, where THE is still observed. This observation excludes the two-channel explanation of THE and provides evidence for the existence of skyrmions in ultrathin SrRuO3.