Oxygen Vacancy-Induced Topological Hall effect in a Nonmagnetic Band Insulator

TL;DR

This paper demonstrates that oxygen vacancies in a nonmagnetic insulator, KTaO3, induce a topological Hall effect through defect-engineered spin textures, revealing a new pathway for topological phenomena in materials.

Contribution

It introduces oxygen vacancy engineering as a method to realize topological Hall effects in nonmagnetic insulators, supported by experimental and theoretical evidence.

Findings

Oxygen vacancies induce topological Hall effect in KTaO3.

Spin-orbit coupling and Rashba effects are crucial for the observed phenomena.

Magnetic polarons form around vacancies, leading to noncollinear spin textures.

Abstract

The discovery of skyrmions has sparked tremendous interests about topologically nontrivial spin textures in recent times. The signature of noncoplanar nature of magnetic moments can be observed as topological Hall effect (THE) in electrical measurement. Realization of such nontrivial spin textures in new materials and through new routes is an ongoing endeavour due to their huge potential for future ultra-dense low-power memory applications. In this work, we report oxygen vacancy (OV) induced THE and anomalous Hall effect (AHE) in a 5$d^0$ system KTaO$_3$. The observation of weak antilocalization behavior and THE in the same temperature range strongly implies the crucial role of spin-orbit coupling (SOC) behind the origin of THE. Ab initio calculations reveal the formation of the magnetic moment on Ta atoms around the OV and Rashba-type spin texturing of conduction electrons. In the presence of Rashba SOC, the local moments around vacancy can form bound magnetic polarons (BMP) with noncollinear spin texture, resulting THE. Scaling analysis between transverse and longitudinal resistance establishes skew scattering driven AHE in present case. Our study opens a route to realize topological phenomena through defect engineering.