Delocalization by Disorder in Layered Systems

TL;DR

This paper investigates how disorder affects electron delocalization in layered materials, revealing that bulk disorder can induce finite out-of-plane conductivity and alter frequency-dependent conductivity behavior.

Contribution

It introduces a simple layered model with potential barriers and impurities, providing analytical and numerical solutions that show disorder-driven delocalization effects.

Findings

Out-of-plane conductivity is localized without bulk disorder.

Bulk disorder leads to finite out-of-plane conductivity.

The ac conductivity exhibits a non-Drude maximum at the scattering frequency.

Abstract

Motivated by anomalously large conductivity anisotropy in layered materials, we propose a simple model of randomly spaced potential barriers (mimicking stacking faults) with isotropic impurities in between the barriers. We solve this model both numerically and analytically, by utilizing an exact solution for the conductivity of a one-dimensional (1D) disordered system. In the absence of bulk disorder, electron motion in the out-of-plane direction is localized. Bulk disorder destroys 1D localization. As a result, the out-of-plane conductivity is finite and scales linearly with the scattering rate by bulk impurities until planar and bulk disorder become comparable. The \emph{ac} out-of-plane conductivity is of a manifestly non-Drude form, with a maximum at the frequency corresponding to the scattering rate by potential barriers.