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We report electrical measurements of the current-induced spin polarization of the surface current in topological insulator devices where contributions from bulk and surface conduction can be disentangled by electrical gating. The devices use a ferromagnetic tunnel junction (permalloy/Al2O3) as a spin detector on a back-gated (Bi,Sb)2Te3 channel. We observe hysteretic voltage signals as the magnetization of the detector ferromagnet is switched parallel or antiparallel to the spin polarization of the surface current. The amplitude of the detected voltage change is linearly proportional to the applied dc bias current in the (Bi,Sb)2Te3 channel. As the chemical potential is tuned from the bulk bands into the surface state band, we observe an enhancement of the spin-dependent voltages up to 300% within the range of the electrostatic gating. Using a simple model, we extract the spin polarization near charge neutrality (i.e., the Dirac point).
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Oct 20 2015|
Bibliographical noteFunding Information:
This study was supported by the Natural Science Foundation of Liaoning Province (2020-MS-204) and the National Natural Science Foundation of China (No. 31701738). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The following grant information was disclosed by the authors: Natural Science Foundation of Liaoning Province (2020-MS-204). National Natural Science Foundation of China: 31701738.
© 2015 American Physical Society. ©2015 American Physical Society.
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