Dual-gate operation of Aharonov-Bohm oscillations in topological insulator nanoribbons

Abstract

Topological insulator (TI) consists of an insulating bulk state and a gapless spin-textured surface state, which enables highly coherent charge and spin transport. When the axial magnetic field is applied to the TI nanoribbon (NR), the topological surface state is evidenced by magnetoconductance (MC) oscillations with a flux period of h/e and h/2e, corresponding to Aharonov-Bohm (AB) and Altshyler-Aronov-Spivak (AAS) oscillations, respectively. The chemical potential of the TI NR can be uniformly controlled via dual gate scheme including top and back gate electrodes. Here, we report the dual gate operation of the axialMC in the TI NR at low temperatures. The gate voltage dependence of the MC curves exhibited a checker-board-like pattern, indicating an existence of the topological surface states in TI NR. The fast Fourier transform (FFT) of the MC curves revealed two different oscillations corresponding to AB and AAS oscillations. Dual gate operation enabled us to change the chemical potential uniformly for both top and bottom surfaces of TI NR, resulting monotonously decreasing behaviors of the peak heights of the ensemble-averaged FFT. We obtained the Fermi velocity and phase coherence length from the temperature dependence of the ensemble-averaged FFT of the MC curves. This work would be useful to explore quantum interference effect in TI NR and develop topolo gical quantum devices.