Coulomb Gap in Graphene Nanoribbons

TL;DR

This paper studies how disorder-induced quantum dots affect conductance in graphene nanoribbons, revealing Coulomb gap behavior and various transport regimes depending on temperature, density, and aspect ratio.

Contribution

It provides a detailed analysis of Coulomb gap effects and transport mechanisms in disordered graphene nanoribbons, highlighting the role of quantum dots and temperature-dependent behavior.

Findings

Conductance dominated by disorder-induced quantum dots.

Coulomb gap manifests as density-dependent activation energy.

Transport transitions from cotunneling to activated regimes with temperature.

Abstract

We investigate the density and temperature-dependent conductance of graphene nanoribbons with varying aspect ratio. Transport is dominated by a chain of quantum dots forming spontaneously due to disorder. Depending on ribbon length, electron density, and temperature, single or multiple quan- tum dots dominate the conductance. Between conductance resonances cotunneling transport at the lowest temperatures turns into activated transport at higher temperatures. The density-dependent activation energy resembles the Coulomb gap in a quantitative manner. Individual resonances show signatures of multi-level transport in some regimes, and stochastic Coulomb blockade in others.