Disorder induced quantized conductance with fractional value and universal conductance fluctuation in three-dimensional topological insulators

TL;DR

This paper theoretically demonstrates that three-dimensional topological insulators exhibit quantized conductance with fractional values and universal conductance fluctuations in the presence of disorder, supported by extensive numerical simulations.

Contribution

It reveals the fractional quantization of conductance and universal conductance fluctuation in 3D topological insulators under disorder, with specific conductance values for different modes.

Findings

Quantized conductance values: 1, 4/3, 6/5 for different modes.

Universal conductance fluctuation approximately 0.5.

Conductance quantization explained by mode mixing theory.

Abstract

We report a theoretical investigation on the conductance and its fluctuation of three-dimensional topological insulators (3D TI) in $Bi_2Se_3$ and $Sb_2Te_3$ in the presence of disorders. Extensive numerical simulations are carried out. We find that in the diffusive regime the conductance is quantized with fractional value. Importantly, the conductance fluctuation is also quantized with a universal value. For 3D TI connected by two terminals, three independent conductances $G_{zz}$, $G_{xx}$ and $G_{zx}$ are identified where z is the normal direction of quintuple layer of 3D TI (see inset of Fig.1). The quantized conductance are found to be $<G_{zz}>=1$, $<G_{xx}>=4/3$ and $<G_{zx}>=6/5$ with corresponding quantized conductance fluctuation 0.54, 0.47, and 0.50. The quantization of average conductance and its fluctuation can be understood by theory of mode mixing. The experimental realization that can observe the quantization of average conductance is discussed.