Direct visualization of current-induced spin accumulation in topological insulators

TLDR

Charge‑to‑spin conversion in various material systems underpins the fundamental understanding of spin‑orbitronics and enables efficient magnetization manipulation. The study directly images current‑induced spin accumulation at the edges of Bi₂Se₃ and BiSbTeSe₂ topological insulators using a scanning photovoltage microscope at room temperature. Using the same microscope, the authors image current‑induced spin accumulation at the edges of Bi₂Se₃, BiSbTeSe₂, and Pt, all at room temperature. The measured out‑of‑plane spin polarization at opposite channel edges reverses with current direction, scales linearly with current magnitude, and yields spin Hall angles of 0.0085 for Bi₂Se₃ and 0.0616 for BiSbTeSe₂, demonstrating optically detectable current‑induced spin accumulation and suggesting spin–light interaction insights.

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.