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

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

Research output: Contribution to journalArticle

41 Citations (Scopus)

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

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Spin polarization
Chemical potential
Induced currents
insulators
Electric potential
polarization
Detectors
Bias currents
Tunnel junctions
Surface states
electric potential
Electrostatics
Magnetization
detectors
Permalloys (trademark)
tunnel junctions
electrical measurement
electrostatics
conduction
magnetization

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

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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).",
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Mapping the chemical potential dependence of current-induced spin polarization in a topological insulator. / Lee, Joon Sue; Richardella, Anthony Raymond; Hickey, Danielle Reifsnyder; Mkhoyan, K. Andre; Samarth, Nitin.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 92, No. 15, 155312, 20.10.2015.

Research output: Contribution to journalArticle

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