Competition between Weak Localization and Antilocalization of Dirac-like Fermions in a Spin-Polarized Two-Dimensional Electron Gas at KTaO3 (111) Interface

TL;DR

This study explores the interplay of weak localization and antilocalization in Dirac-like fermions within spin-polarized 2DEGs at KTaO3 interfaces, revealing tunable quantum transport properties influenced by ferromagnetism and spin-orbit coupling.

Contribution

It introduces a novel platform where quantum transport phenomena can be controlled in spin-polarized oxide 2DEGs through optical gating and magnetic effects.

Findings

Evidence of ferromagnetic order in 2DEGs via anomalous Hall effect and magnetoresistance.

Demonstration of tunable competition between WL and WAL through optical gating.

Observation of nontrivial Berry phase effects due to broken time-reversal symmetry.

Abstract

Quantum transport phenomena in two-dimensional electron gases (2DEGs) at oxide interfaces have garnered significant interest owing to their potential in spintronic and quantum information technologies. Here, we systematically investigate the quantum conductance corrections of spin-polarized 2DEGs formed at the interfaces between two insulating oxides, ferromagnetic EuTiO3 (ETO) films and (111)-oriented KTaO3 (KTO) substrates. The anomalous Hall effect and hysteretic magnetoresistance provide clear evidence for long-range ferromagnetic order in the 2DEGs, which could be attributed to interfacial Eu doping in combination with the magnetic proximity effect of the ETO layer. The breaking of time-reversal symmetry by ferromagnetism in the 2DEGs, and with the assistance of spin-orbit coupling effect, gives rise to a nontrivial Berry phase. This results in a competition between weak localization (WL) and weak antilocalization (WAL) in the quantum transport of Dirac-like fermions at the KTO (111) interfaces. Notably, this competitive behavior can be effectively tuned by optical gating via a photoexcitation-induced shift of the Fermi level. Our findings demonstrate a controllable platform based on spin-polarized oxide 2DEGs for quantum transport, opening new avenues for spin-orbitronic and topological electronic applications.