title: Chiral tunneling of topological states: towards the efficient generation of spin current using spin-momentum locking.
abstract: We show that the interplay between chiral tunneling and spin-momentum locking of helical surface states leads to spin amplification and filtering in a 3D topological insulator (TI). Our calculations show that the chiral tunneling across a TI pn junction allows normally incident electrons to transmit, while the rest are reflected with their spins flipped due to spin-momentum locking. The net result is that the spin current is enhanced while the dissipative charge current is simultaneously suppressed, leading to an extremely large, gate-tunable spin-to-charge current ratio (∼20) at the reflected end. At the transmitted end, the ratio stays close to 1 and the electrons are completely spin polarized.
authors.affiliation: Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, USA.
authors.forename: K M Masum
authors.initials: KM
authors.lastname: Habib
authors.affiliation: Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, USA.
authors.forename: Redwan N
authors.initials: RN
authors.lastname: Sajjad
authors.affiliation: Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, USA.
authors.forename: Avik W
authors.initials: AW
authors.lastname: Ghosh