Interpreting current-induced spin polarization in topological insulator surface states

Abstract

Several recent experiments on three-dimensional topological insulators claim to observe a large charge current-induced non-equilibrium ensemble spin polarization of electrons in the helical surface state. We present a comprehensive criticism of such claims, using both theory and experiment: First, we clarify the interpretation of quantities extracted from these measurements by deriving standard expressions from a Boltzmann transport equation approach in the relaxation-time approximation at zero and finite temperature to emphasize our assertion that, despite high in-plane spin projection, obtainable current-induced ensemble spin polarization is minuscule. Second, we use a simple experiment to demonstrate that magnetic field-dependent open-circuit voltage hysteresis (identical to those attributed to current-induced spin polarization in topological insulator surface states) can be generated in analogous devices where current is driven through thin films of a topologically-trivial metal. This result *ipso facto* discredits the naive interpretation of previous experiments with TIs, which were used to claim observation of helicity, i.e. spin-momentum locking in the topologically-protected surface state.

References in corpus (18)

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• Direct electronic measurement of the spin Hall effect
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• Electrical injection and detection of spin-polarized currents in topological insulator Bi2Te2Se
• Mapping the chemical potential dependence of current-induced spin polarization in a topological insulator
• Symmetry, distorted bandstructure, and spin-orbit coupling of (group-III) metal-monochalcogenide monolayers
• Nonequilibrium spin texture within a thin layer below the surface of current-carrying topological insulator Bi${}_2$Se${}_3$: A first-principles quantum transport study
• Proposal for a Topological Plasmon Spin Rectifier
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Cited by in corpus (12)

• Large multi-directional spin-to-charge conversion in low symmetry semimetal MoTe${}_2$ at room temperature
• Switching of Charge-Current-Induced Spin Polarization in the Topological Insulator BiSbTeSe2
• Omnidirectional spin-to-charge conversion in graphene/NbSe${}_2$ van der Waals heterostructures
• Transmission Line Model for Materials with Spin-Momentum Locking
• Electrical detection of surface spin polarization of candidate topological Kondo insulator SmB6
• Topological insulator spin transistor
• Band tilt induced nonlinear Nernst effect in topological insulators: An efficient generation of high-performance spin polarization
• Resonant Tunneling Anisotropic Magnetoresistance Induced by Magnetic Proximity
• The influence of anisotropic Rashba spin-orbit coupling on current-induced spin polarization in graphene
• Anomalously large spin-current voltages on the surface of SmB${}_6$
• Unidirectional magneto-transport of linearly dispersing topological edge states
• Promoted current-induced spin polarization in inversion symmetry broken topological insulator thin films