Efficient Charge-Spin Conversion and Magnetization Switching though Rashba Effect at Topological Insulator/Ag Interface

TL;DR

This study demonstrates highly efficient charge-spin conversion and magnetization switching at a topological insulator/Ag interface, driven by Rashba effect and interfacial phenomena, with potential applications in spintronic devices.

Contribution

It reveals the dominant interfacial Rashba effect in charge-spin conversion and reports the first demonstration of Rashba-induced magnetization switching in this system.

Findings

Charge-to-spin conversion ratio reaches 0.5 at 5 nm Ag thickness.

Interfacial Rashba effect surpasses topological surface states in contribution.

Magnetization switching achieved with low current density of 5.8×10^5 A/cm².

Abstract

We report the observation of efficient charge-to-spin conversion in the three-dimensional topological insulator (TI) Bi2Se3 and Ag bilayer by the spin-torque ferromagnetic resonance technique. The spin orbit torque ratio in the Bi2Se3/Ag/CoFeB heterostructure shows a significant enhancement as the Ag thickness increases to ~2 nm and reaches a value of 0.5 for 5 nm Ag, which is ~3 times higher than that of Bi2Se3/CoFeB at room temperature. The observation reveals the interfacial effect of Bi2Se3/Ag exceeds that of the topological surface states (TSS) in the Bi2Se3 layer and plays a dominant role in the charge-to-spin conversion in the Bi2Se3/Ag/CoFeB system. Based on the first-principles calculations, we attribute our observation to the large Rashba-splitting bands which wrap the TSS band and has the same net spin polarization direction as TSS of Bi2Se3. Subsequently, we demonstrate for the first time the Rashba induced magnetization switching in Bi2Se3/Ag/Py with a low current density of 5.8 X 10^5 A/cm2.