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Dephasing-Induced Stabilization of a Perfectly Conducting Channel in Disordered Graphene Nanoribbons with Zigzag Edges

Electron transport in a disordered graphene nanoribbon with zigzag edges is crucially affected by a perfectly conducting channel (PCC), which is stabilized if intervalley scattering is ignorable. In the presence of such a PCC, the dimensionless conductance g of the system decreases to the quantized value of g = 1 with increasing system length L. In the realistic case where intervalley scattering is weak but not ignorable, the PCC is gradually destabilized with increasing L, and g eventually decays to zero owing to the onset of Anderson localization. Here, we show that such destabilization of the PCC can be relaxed by pure dephasing. We numerically calculate g in the presence of long-range impurities, which induce weak intervalley scattering, taking the dephasing effect into account. It is demonstrated that, under sufficient dephasing, the decay of g in the regime of g \lesssim 1 is strongly suppressed and the quasi-quantization of g (i.e., g ~ 1) can be observed in a wide region of L.