title: Effect of surface state hybridization on current-induced spin-orbit torque in thin topological insulator films.
abstract: We investigate the thickness optimization for maximum current-induced spin-orbit torque (SOT) generated by topological surface states (TSS's) in a bilayer system comprising of a ferromagnetic layer coupled to a thin topological insulator (TI) film. We show that by reducing the TI thickness, two competing effects on the SOT are induced: (i) the torque strength is stronger as the bulk contribution is decreased; (ii) on the other hand, the torque strength becomes suppressed due to increasing hybridization of the surface states. The latter is attributed to the opposite helicities of the coupled TSS's. We theoretically model the interplay of these two effects and derive the optimal TI thickness to maximize the spin torque, which is estimated to be about 3-5 nm for typical Bi2Se3films.
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117576, Singapore. elehcs@nus.edu.sg.
authors.forename: Cong Son
authors.initials: CS
authors.lastname: Ho
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117576, Singapore.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117576, Singapore.
authors.forename: Zhou Bin
authors.identifier: http://orcid.org/0000-0002-7056-937X
authors.initials: ZB
authors.lastname: Siu
authors.affiliation: Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, 08-01, Innovis, Singapore.
authors.forename: Seng Ghee
authors.initials: SG
authors.lastname: Tan
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117576, Singapore.
authors.forename: Mansoor B A
authors.initials: MBA
authors.lastname: Jalil
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117576, Singapore.
authors.forename: Hyunsoo
authors.initials: H
authors.lastname: Yang