title: Giant Spin Pumping and Inverse Spin Hall Effect in the Presence of Surface and Bulk Spin-Orbit Coupling of Topological Insulator Bi2Se3.
abstract: Three-dimensional (3D) topological insulators are known for their strong spin-orbit coupling (SOC) and the existence of spin-textured surface states that might be potentially exploited for "topological spintronics." Here, we use spin pumping and the inverse spin Hall effect to demonstrate successful spin injection at room temperature from a metallic ferromagnet (CoFeB) into the prototypical 3D topological insulator Bi2Se3. The spin pumping process, driven by the magnetization dynamics of the metallic ferromagnet, introduces a spin current into the topological insulator layer, resulting in a broadening of the ferromagnetic resonance (FMR) line width. Theoretical modeling of spin pumping through the surface of Bi2Se3, as well as of the measured angular dependence of spin-charge conversion signal, suggests that pumped spin current is first greatly enhanced by the surface SOC and then converted into a dc-voltage signal primarily by the inverse spin Hall effect due to SOC of the bulk of Bi2Se3. We find that the FMR line width broadens significantly (more than a factor of 5) and we deduce a spin Hall angle as large as 0.43 in the Bi2Se3 layer.
authors.affiliation: Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Jamali
authors.affiliation: Department of Physics, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Joon Sue
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Jong Seok
authors.initials: JS
authors.lastname: Jeong
authors.affiliation: Department of Physics, California State University , Northridge, California 91330-8268, United States.
authors.forename: Farzad
authors.initials: F
authors.lastname: Mahfouzi
authors.affiliation: Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Lv
authors.affiliation: Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Zhengyang
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716-2570, United States.
authors.forename: Branislav K
authors.initials: BK
authors.lastname: Nikolić
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: K Andre
authors.initials: KA
authors.lastname: Mkhoyan
authors.affiliation: Department of Physics, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Nitin
authors.initials: N
authors.lastname: Samarth
authors.affiliation: Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Wang
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D012643:Selenium; D001729:Bismuth
keywords: TEM; Topological−insulator/ferromagnet heterostructures; ferromagnetic resonance; interface intermixing; interfacial spin−orbit coupling; spin Hall effect; spin pumping; spintronics