High Spin to Charge Conversion Efficiency in Electron Beam-Evaporated Topological Insulator Bi₂Se₃

Bi₂Se₃ is a well-established topological insulator (TI) having spin momentum locked Dirac surface states at room temperature and predicted to exhibit high spin to charge conversion efficiency (SCCE) for spintronics applications. The SCCE in TIs is characterized by an inverse Edelstein effect length (λ_IREE). We report an λ_IREE of ∼0.36 nm, which is the highest ever observed in Bi₂Se₃. Here, we performed spin pumping and inverse spin Hall effect (ISHE) in an electron beam-evaporated Bi₂Se₃/CoFeB bilayer. The Bi₂Se₃ thickness dependence of λ_IREE, perpendicular surface anisotropy (K_S), spin mixing conductance, and spin Hall angle confirmed that spin to charge conversion is due to spin momentum locked Dirac surface states. We propose that the role of surface states in SCCE can be understood by the evaluation of K_S. The SCCE is found to be high when the value of K_S is small.