Mapping the chemical potential dependence of current-induced spin polarization in a topological insulator

Joon Sue Lee, Anthony Richardella, Danielle Reifsnyder Hickey, K. Andre Mkhoyan, Nitin Samarth

Research output: Contribution to journalArticle

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Abstract

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 languageEnglish (US)
Article number155312
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume92
Issue number15
DOIs
StatePublished - Oct 20 2015

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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