Temperature dependent spin pumping into the topological insulator Bi₂Te₃

The bismuth and antimony - based three dimensional (3-D) topological insulators (TIs) such as Bi₂Te₃, Sb₂Te₃, BiSb display robust spin-to-charge conversion properties due to their conducting topological surface states (TSS) [1]. Here, we report measurements of ferromagnetic resonance (FMR) driven spin pumping from an amorphous ferromagnet (FM) Fe₆₀Co₂₀B₂₀ (FeCoB) into the 3-D TI-Bi₂Te₃. The FMR induced spin pumping is reflected in the enhanced Gilbert damping of precessing magnetization and a dc voltage (V_dc) developed across the sample at resonance. The observed V_dc signal is a superposition of spin rectification effects (SRE), inverse spin Hall effect (ISHE) and inverse Rashba Edelstein effect (IREE). We have measured the V_dc in such a manner that the spin injection direction is reversed by flipping the sample to separate SRE and ISHE signals, which are even and odd functions of spin injection directions respectively. The role of TSS has been evaluated by measuring FMR and ISHE signals at cryogenic temperatures. It has been observed that the IREE effect is enhanced when a thin layer of silver is sandwiched between the FeCoB and Bi₂Te₃.

1. Hasan, M. Zahid, and Joel E. Moore. "Three-dimensional topological insulators." Annu. Rev. Condens. Matter Phys. 2.1 (2011): 55-78.