Topological Surface States Originated Spin-Orbit Torques in Bi2Se3

TL;DR

This study demonstrates that topological surface states in Bi2Se3 significantly enhance spin-orbit torques, especially at low temperatures, indicating potential for efficient spin current sources in spintronics.

Contribution

We experimentally show that topological surface states in Bi2Se3 are the primary origin of enhanced spin-orbit torques, with a temperature-dependent increase in torque ratio.

Findings

Spin-orbit torque ratio increases from ~0.047 at 300K to ~0.42 below 50K.

Significant out-of-plane torque observed at low temperatures.

Topological surface states are identified as the main source of observed torques.

Abstract

Three dimensional topological insulator bismuth selenide (Bi2Se3) is expected to possess strong spin-orbit coupling and spin-textured topological surface states, and thus exhibit a high charge to spin current conversion efficiency. We evaluate spin-orbit torques in Bi2Se3/Co40Fe40B20 devices at different temperatures by spin torque ferromagnetic resonance measurements. As temperature decreases, the spin-orbit torque ratio increases from ~ 0.047 at 300 K to ~ 0.42 below 50 K. Moreover, we observe a significant out-of-plane torque at low temperatures. Detailed analysis indicates that the origin of the observed spin-orbit torques is topological surface states in Bi2Se3. Our results suggest that topological insulators with strong spin-orbit coupling could be promising candidates as highly efficient spin current sources for exploring next generation of spintronic applications.