Observation of Quantum Hall effect in an ultra-thin (Bi0.53Sb0.47)2Te3 film

We report the observation of the Quantum Hall effect from the topological surface states in both the Dirac electron and Dirac hole regions in a 4 quintuple layer (Bi0.53Sb0.47)2Te3 film grown on GaAs (111)B substrates. The Fermi level is sitting within the enlarged bulk band gap due to the quantum confinement of the ultra-thin film and can be tuned through the Dirac point by gate biases. Furthermore, the Hall resistance Rxy shows even denominator plateaus, which could be fractional Quantum Hall states. This may be due to the hybridization between the top and bottom surface states and suggests the possible way to manipulate the interaction of two surfaces for potential spintronic devices.