Conductance of Disordered Wires with Unitary Symmetry: Role of Perfectly Conducting Channels

Abstract

We study the conductance of disordered quantum wires with unitary symmetry focusing on the case where m excess one-way conducting channels are present. The excess channels make the channel number in one direction by m greater than that in the opposite direction, resulting in the stabilization of m perfectly conducting channels. The case of m=1 can be realized in zigzag nanographene ribbons. Due to the presence of perfectly conducting channels, the dimensionless conductance g behaves as g→m with increasing system length, indicating the absence of the Anderson localization. To describe the anomalous behavior, we generalize the unitary class to allow m excess one-way channels and derive the corresponding Fokker–Planck equation for transmission eigenvalues. It is shown that the conductance decay length is reduced with increasing m. We present an extended classification table for the standard three classes.