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Robust non-integer conductance in disordered 2D Dirac semimetals

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.