Conductance distributions in disordered quantum spin-Hall systems

TL;DR

This paper investigates the conductance distributions in disordered quantum spin-Hall systems, revealing that critical conductance distributions depend on boundary conditions and edge states, with notable fluctuations even in quantized regimes.

Contribution

It provides the first detailed numerical analysis of conductance distributions in disordered QSH systems, highlighting their sensitivity to boundary conditions and edge states.

Findings

Conductance distribution differs at metal-QSH and metal-ordinary insulator transitions.

Edge states influence the critical conductance distribution.

Large fluctuations occur in point-contact conductance despite quantized two-terminal conductance.

Abstract

We study numerically the charge conductance distributions of disordered quantum spin-Hall (QSH) systems using a quantum network model. We have found that the conductance distribution at the metal-QSH insulator transition is clearly different from that at the metal-ordinary insulator transition. Thus the critical conductance distribution is sensitive not only to the boundary condition but also to the presence of edge states in the adjacent insulating phase. We have also calculated the point-contact conductance. Even when the two-terminal conductance is approximately quantized, we find large fluctuations in the point-contact conductance. Furthermore, we have found a semi-circular relation between the average of the point-contact conductance and its fluctuation.