paper

Spin-orbitronics at a topological insulator-semiconductor interface

arXiv:1911.10611 · doi:10.1103/PhysRevB.101.184406

Abstract

Topological insulators (TIs) hold great promises for new spin-related phenomena and applications thanks to the spin texture of their surface states. However, a versatile platform allowing for the exploitation of these assets is still lacking due to the difficult integration of these materials with the mainstream Si-based technology. Here, we exploit germanium as a substrate for the growth of Bi $_{2}$ Se $_{3}$ , a prototypical TI. We probe the spin properties of the Bi $_{2}$ Se $_{3}$ /Ge pristine interface by investigating the spin-to-charge conversion taking place in the interface states by means of a non-local detection method. The spin population is generated by optical orientation in Ge, and diffuses towards the Bi $_{2}$ Se $_{3}$ which acts as a spin detector. We compare the spin-to-charge conversion in Bi $_{2}$ Se $_{3}$ /Ge with the one taking place in Pt in the same experimental conditions. Notably, the sign of the spin-to-charge conversion given by the TI detector is reversed compared to the Pt one, while the efficiency is comparable. By exploiting first-principles calculations, we ascribe the sign reversal to the hybridization of the topological surface states of Bi $_{2}$ Se $_{3}$ with the Ge bands. These results pave the way for the implementation of highly efficient spin detection in TI-based architectures compatible with semiconductor-based platforms.

5 pages and 5 figures