Quantum Hall Effect on Top and Bottom Surface States of Topological Insulator (Bi1-xSbx)2Te3 Films

TL;DR

This paper demonstrates the quantum Hall effect on the surface states of (Bi1-xSbx)2Te3 topological insulator films, showing quantized resistance and novel surface state phenomena under magnetic fields and electrostatic gating.

Contribution

It reports the first observation of quantum Hall states on the top and bottom surface Dirac states of (Bi1-xSbx)2Te3 films with gate tuning, revealing new surface state physics.

Findings

Quantum Hall states with b1 1 filling factor observed

Quantized Hall resistance of h/e^2 measured

A b0=0 state indicating a pseudo-spin Hall insulator

Abstract

The three-dimensional (3D) topological insulator (TI) is a novel state of matter as characterized by two-dimensional (2D) metallic Dirac states on its surface. Bi-based chalcogenides such as Bi2Se3, Bi2Te3, Sb2Te3 and their combined/mixed compounds like Bi2Se2Te and (Bi1-xSbx)2Te3 are typical members of 3D-TIs which have been intensively studied in forms of bulk single crystals and thin films to verify the topological nature of the surface states. Here, we report the realization of the Quantum Hall effect (QHE) on the surface Dirac states in (Bi1-xSbx)2Te3 films (x = 0.84 and 0.88). With electrostatic gate-tuning of the Fermi level in the bulk band gap under magnetic fields, the quantum Hall states with filling factor \nu = \pm 1 are resolved with quantized Hall resistance of Ryx = h/e2 and zero longitudinal resistance, owing to chiral edge modes at top/bottom surface Dirac states. Furthermore, the appearance of a \nu = 0 state (\sigma xy = 0) reflects a pseudo-spin Hall insulator state when the Fermi level is tuned in between the energy levels of the non-degenerate top and bottom surface Dirac points. The observation of the QHE in 3D TI films may pave a way toward TI-based electronics.