Large Tunable Spin-to-Charge Conversion Induced by Hybrid Rashba and Dirac Surface States in Topological Insulator Heterostructures

Abstract

Topological insulators (TIs) have emerged as some of the most efficient spin-to-charge convertors because of their correlated spin-momentum locking at helical Dirac surface states. While endeavors have been made to pursue large "charge-to-spin" conversions in novel TI materials using spin-torque-transfer geometries, the reciprocal process "spin-to-charge" conversion, characterized by the inverse Edelstein effect length (λ_IEE) in the prototypical TI material (Bi₂Se₃), remains moderate. Here, we demonstrate that, by incorporating a "second" spin-splitting band, namely, a Rashba interface formed by inserting a bismuth interlayer between the ferromagnet and the Bi₂Se₃ (i.e., ferromagnet/Bi/Bi₂Se₃ heterostructure), λ_IEE shows a pronounced increase (up to 280 pm) compared with that in pure TIs. We found that λ_IEE alters as a function of bismuth interlayer thickness, suggesting a new degree of freedom to manipulate λ_IEE by engineering the interplay of Rashba and Dirac surface states. Our finding launches a new route for designing TI- and Rashba-type quantum materials for next-generation spintronic applications.