Flux-driven delocalization transition in disordered topological insulator nanowires

Abstract

Topological insulator nanowires provide a tunable platform for studying the interplay between disorder, quantum interference, and symmetry-protected transport. Here we investigate quantum transport in disordered topological insulator nanowires threaded by an axial magnetic flux. By computing the conductance as a function of wire length, magnetic flux, chemical potential, and disorder strength, we extract the localization length to characterize the flux-driven delocalization transition near half-integer flux quanta. We find that the localization length diverges with a robust critical exponent $ν=2$, independent of the chemical potential and disorder strength considered here. This exponent differs from that of the integer quantum Hall transition, pointing to distinct scaling behavior. Near integer flux quanta, we further find that the conductance evolves from a weak-localization dip at low chemical potential to a weak anti-localization peak at higher chemical potential, which splits and is eventually suppressed as the system crosses over to the strongly localized regime.