Spin to Charge Current Conversion in the Topological Insulator (Bi_0.22Sb_0.78)₂Te₃ Films at Room Temperature

Topological Insulators (TIs) constitute a new class of quantum materials, and here we report spin to charge current conversion in an intrinsic TI (Bi_0.22Sb_0.78)₂Te₃ film at room temperature. The spin currents are generated in a thin layer of permalloy (Py) by two different processes, spin pumping effect (SPE) and spin Seebeck effect (SSE). In the first process, we use microwave-driven ferromagnetic resonance of the Py film to generate a SPE spin current that is injected into the TI (Bi_0.22Sb_0.78)₂Te₃ layer in direct contact with Py. In the second process, we use the SSE in the longitudinal configuration in Py without contamination by the Nernst effect made possible with the use of a thin NiO layer between the Py and (Bi_0.22Sb_0.78)₂Te₃ layers. The spin-to-charge current conversion is attributed to the inverse Edelstein effect (IEE) by the spin-momentum locking in the electron Fermi contours due to the Rashba field. The measurements by the two techniques yield very similar values for the IEE parameter, which are larger than the reported values in the previous studies on TIs.