Robust non-integer conductance in disordered 2D Dirac semimetals

Abstract

Abstract We study the conductance G of 2D Dirac semimetal nanowires at the presence of disorder. For an even nanowire length L determined by the number of unit cells, we find non-integer values for G that are independent of L and persist with weak disorder, indicated by the vanishing fluctuations of G. The effect is created by a combination of the scattering effects at the contacts (interface) between the leads and the nanowire, an energy gap present in the nanowire for even L and the topological properties of the 2D Dirac semimetals. Unlike conventional materials the reduced G due to the scattering at the interface, is stabilized at non-integer values inside the nanowire, leading to a topological phase for weak disorder. For strong disorder the system leaves the topological phase and the fluctuations of G are increased as the system undergoes a transition/crossover toward the Anderson localized (insulating) phase, via a non-standard disordered phase. We study the scaling and the statistics of G at these phases. In addition we have found that the effect of robust non-integer G disappears for odd L, which results in integer G, determined by the number of open channels in the nanowire, due to resonant scattering.