Origin and evolution of surface spin current in topological insulators

André Dankert; Priyamvada Bhaskar; Dmitrii Khokhriakov; Isabel Harrysson Rodrigues; Bogdan Karpiak; Venkata Kamalakar Mutta; Sophie Charpentier; Ion Garate; Saroj Prasad Dash

doi:10.1103/PhysRevB.97.125414

Origin and evolution of surface spin current in topological insulators
Journal article, 2018

The Dirac surface states of topological insulators offer a unique possibility for creating spin polarized charge currents due to the spin-momentum locking. Here we demonstrate that the control over the bulk and surface contribution is crucial to maximize the charge-to-spin conversion efficiency. We observe an enhancement of the spin signal due to surface-dominated spin polarization while freezin g out the bulk conductivity in semiconducting Bi1.5Sb0.5Te1.7Se1.3 below 100K. Detailed measurements up to room temperature exhibit a strong reduction of the magnetoresistance signal between 2and100K, which we attribute to the thermal excitation of bulk carriers and to the electron-phonon coupling in the surface states. The presence and dominance of this effect up to room temperature is promising for spintronic science and technology.