Charge and Spin Transport in Edge Channels of aν=0Quantum Hall System on the Surface of Topological Insulators

Abstract

Three-dimensional topological insulators of finite thickness can show the quantum Hall effect (QHE) at the filling factor ν = 0 under an external magnetic field if there is a finite potential difference between the top and bottom surfaces. We calculate energy spectra of surface Weyl fermions in the ν = 0 QHE and find that gapped edge states with helical spin structure are formed from Weyl fermions on the side surfaces under certain conditions. These edge channels account for the nonlocal charge transport in the ν = 0 QHE which is observed in a recent experiment on (Bi1−xSbx)2Te3 films. The edge channels also support spin transport due to the spin-momentum locking. We propose an experimental setup to observe various spintronics functions such as spin transport and spin conversion.Introduction -The quantum Hall effect (QHE) is a representative topological quantum phenomenon where edge channels play an essential role in low-energy transport [1,2]. The emergence of gapless edge channels is closely tied to nontrivial topology of gapped electronic states in the bulk, which is the property called bulk-edge correspondence. For topological insulators (TIs) [3,4], the bulk-edge correspondence dictates that any surface of a three-dimensional (3D) TI with a nontrivial Z 2 index has a single (or an odd number of) flavor(s) of Weyl fermions with spin-momentum locking. The surface Weyl fermions are predicted to give a variety of novel phenomena such as the quantized topological magneto-electric (ME) effect [5] and monopole-like magnetic field distribution induced by a point charge [6]. Another remarkable phenomenon is the quantized anomalous Hall effect without an external magnetic field [7][8][9][10]. By contrast, in an external magnetic field, a single flavor of Weyl fermions are expected to show a "half-integer" QHE with the Hall conductance σ xy = (n +

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