title: Spin generation via bulk spin current in three-dimensional topological insulators.
abstract: To date, spin generation in three-dimensional topological insulators is primarily modelled as a single-surface phenomenon, attributed to the momentum-spin locking on each individual surface. In this article, we propose a mechanism of spin generation where the role of the insulating yet topologically non-trivial bulk becomes explicit: an external electric field creates a transverse pure spin current through the bulk of a three-dimensional topological insulator, which transports spins between the top and bottom surfaces. Under sufficiently high surface disorder, the spin relaxation time can be extended via the Dyakonov-Perel mechanism. Consequently, both the spin generation efficiency and surface conductivity are largely enhanced. Numerical simulation confirms that this spin generation mechanism originates from the unique topological connection of the top and bottom surfaces and is absent in other two-dimensional systems such as graphene, even though they possess a similar Dirac cone-type dispersion.
authors.affiliation: Department of Physics, University of California, One Shields Avenue, California 95616, USA.
authors.forename: Xingyue
authors.initials: X
authors.lastname: Peng
authors.affiliation: Department of Physics, University of California, One Shields Avenue, California 95616, USA.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Physics, University of California, One Shields Avenue, California 95616, USA.
authors.forename: Rajiv R P
authors.initials: RR
authors.lastname: Singh
authors.affiliation: Department of Physics, University of California, One Shields Avenue, California 95616, USA.
authors.forename: Sergey Y
authors.initials: SY
authors.lastname: Savrasov
authors.affiliation: Department of Physics, University of California, One Shields Avenue, California 95616, USA.
authors.forename: Dong
authors.initials: D
authors.lastname: Yu