Universal Conductance Fluctuation in Two-Dimensional Topological Insulators.

Duk-Hyun Choe,K J Chang

doi:10.1038/srep10997

Abstract

Despite considerable interest in two-dimensional (2D) topological insulators (TIs), a fundamental question still remains open how mesoscopic conductance fluctuations in 2D TIs are affected by spin-orbit interaction (SOI). Here, we investigate the effect of SOI on the universal conductance fluctuation (UCF) in disordered 2D TIs. Although 2D TI exhibits UCF like any metallic systems, the amplitude of these fluctuations is distinguished from that of conventional spin-orbit coupled 2D materials. Especially, in 2D systems with mirror symmetry, spin-flip scattering is forbidden even in the presence of strong intrinsic SOI, hence increasing the amplitude of the UCF by a factor of compared with extrinsic SOI that breaks mirror symmetry. We propose an easy way to experimentally observe the existence of such spin-flip scattering in 2D materials. Our findings provide a key to understanding the emergence of a new universal behavior in 2D TIs.

Highlights

Adsorption of transition metal adatoms[29,30,31,32], and proximity-induced effects[33,34,35,36,37,38]
To identify the one-dimensional edge state, we consider two armchair graphene nanoribbons (N-aGNRs) of about 10 nm width, where N is the number of C-C dimer lines across the ribbon
In the strong coupling regime, the band gaps of both aGNRs increase to 0.95 eV due to the SOI, and the topological edge states appear in the gaps [Fig. 1(a,b)]

Summary

Introduction

Adsorption of transition metal adatoms[29,30,31,32], and proximity-induced effects[33,34,35,36,37,38]. In the diffusive transport regime below –0.5 eV, regardless of the channel energy, disorder type, and disorder strength, the conductance fluctuation exhibits the universal behavior with the UCF value of 0.52 e2/h.

Results

Conclusion