Direct visualization of current induced spin accumulation in topological insulators

TL;DR

This study visualizes current-induced spin accumulation at the edges of topological insulators using a scanning photovoltage microscope, revealing spin polarization behavior and quantifying spin Hall angles at room temperature.

Contribution

It provides the first direct spatial imaging of spin accumulation in topological insulators at room temperature, advancing understanding of charge-to-spin conversion mechanisms.

Findings

Spin polarization is out-of-plane with opposite signs at channel edges.

Spin signal reverses with current direction, linear with current magnitude.

Spin Hall angles are quantified for Bi2Se3 and BiSbTeSe2.

Abstract

Charge-to-spin conversion in various material systems is the key for the fundamental understanding of spin-orbitronis as well as the development of efficient means to manipulate the magnetization. We report the direct spatial imaging of current induced spin accumulation at the channel edges of Bi2Se3 and BiSbTeSe2 topological insulators by a scanning photovoltage microscope at room temperature. The spin polarization is along the out-of-plane direction with opposite signs for the two channel edges. The accumulated spin direction reverses sign upon changing the current direction and the detected spin signal shows a linear dependence on the magnitude of currents, which indicates that our observed phenomena are the current induced effects. The spin Hall angle of Bi2Se3 and BiSbTeSe2 is determined to be 0.0085 and 0.0616, respectively. We further image the current induced spin accumulation in a Pt heavy metal. Our results open up the possibility of optically detecting the current induced spin accumulations, and thus point towards a better understanding of the interaction between spins and circularly polarized light.