Gate-tunable Rashba spin-orbit coupling and spin polarization at diluted oxide interfaces

TL;DR

This study demonstrates gate-tunable Rashba spin-orbit coupling and spin polarization at LaAl1-xMnxO/SrTiO3 interfaces, revealing how Mn doping influences spin splitting and carrier density, opening new avenues for spintronic applications.

Contribution

It introduces the first observation of tunable Rashba SOC and spin polarization in LAMO/STO interfaces with variable Mn doping, highlighting the control of spin properties via gating.

Findings

Maximum spin splitting energy decreases with Mn content and vanishes at x=0.3.

A fully back-gate-tunable spin-polarized 2D electron liquid is achieved at x=0.3.

Dome-shaped dependence of spin splitting on carrier density is observed.

Abstract

Diluted oxide interface of LaAl1-xMnxO/SrTiO3 (LAMO/STO) provides a new way of tuning the ground states of the interface between the two band insulators of LAO and STO from metallic/superconducting to highly insulating. Increasing the Mn doping level (x) leads to a delicate control of the carrier density as well as a raise in the electron mobility and spin polarization. Herein, we demonstrate a tunable Rashba spin-orbit coupling (SOC) and spin polarization of LAMO/STO (0.2 <= x <= 0.3) by applying a back gate. The presence of SOC causes the splitting of energy band into two branches by a spin splitting energy. The maximum spin splitting energy depends on the Mn doping and decreases with the increasing Mn content and then vanishes at x = 0.3. The carrier density dependence of the spin splitting energy for different compositions shows a dome-shaped behavior with a maximum at different normalized carrier density. These findings have not yet been observed in LAO/STO interfaces. A fully back-gate-tunable spin-polarized 2DEL is observed at the interface with x = 0.3 where only dxy orbits are populated (5.3E12 cm-2 <= ns <= 1.0E13 cm-2). The present results shed light on unexplored territory in SOC at STO-base oxide heterostructures and make LAMO/STO an intriguing platform for spin-related phenomena in 3d-electron systems.