Two-dimensional spin-filtered chiral network model for the Z_2 quantum spin-Hall effect

TL;DR

This paper introduces a novel two-dimensional spin-filtered chiral network model to study the effects of static disorder on the Z_2 quantum spin-Hall effect, revealing a metallic phase within the insulating phase and characterizing the phase transitions.

Contribution

The paper develops a new network model that differs from previous models by allowing an odd number of Kramers doublets, providing insights into the phase structure of the Z_2 quantum spin-Hall effect.

Findings

Existence of a finite metallic phase within the Z_2 insulating phase.

Quantum phase transitions belong to the symplectic universality class.

The model captures the effects of static disorder on spin-orbit coupled electrons.

Abstract

The effects of static disorder on the Z_2 quantum spin-Hall effect for non-interacting electrons propagating in two-dimensional space is studied numerically. A two-dimensional time-reversal symmetric network model is constructed to account for the effects of static disorder on the propagation of non-interacting electrons subjected to spin-orbit couplings. This network model is different from past network models belonging to the symplectic symmetry class in that the propagating modes along the links of the network can be arranged into an odd number of Kramers doublet. It is found that (1) a two-dimensional metallic phase of finite extent is embedded in a Z_2 insulating phase in parameter space and (2) the quantum phase transitions between the metallic and Z_2 insulating phases belong to the conventional symplectic universality class in two space dimensions.