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 freezing 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 2 and 100K, 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.
@article{arxiv.1804.09930,
title = {Origin and evolution of surface spin current in topological insulators},
author = {André Dankert and Priyamvada Bhaskar and Dmitrii Khokhriakov and Isabel H. Rodrigues and Bogdan Karpiak and M. Venkata Kamalakar and Sophie Charpentier and Ion Garate and Saroj P. Dash},
journal= {arXiv preprint arXiv:1804.09930},
year = {2018}
}