Transport in gapped bilayer graphene: the role of potential fluctuations

TL;DR

This study investigates how potential fluctuations influence electrical transport in gapped bilayer graphene, revealing multiple conduction mechanisms across temperature ranges and emphasizing the role of localized states.

Contribution

The paper introduces a comprehensive model linking potential fluctuations to various conduction processes in gapped bilayer graphene, supported by experimental data.

Findings

Thermally activated conduction dominates above 5 K.

Localized states cause variable-range hopping at low temperatures.

Activation energy approaches half the band gap at large gaps.

Abstract

We employ a dual-gated geometry to control the band gap \Delta in bilayer graphene and study the temperature dependence of the resistance at the charge neutrality point, RNP(T), from 220 to 1.5 K. Above 5 K, RNP(T) is dominated by two thermally activated processes in different temperature regimes and exhibits exp(T3/T)^{1/3} below 5 K. We develop a simple model to account for the experimental observations, which highlights the crucial role of localized states produced by potential fluctuations. The high temperature conduction is attributed to thermal activation to the mobility edge. The activation energy approaches \Delta /2 at large band gap. At intermediate and low temperatures, the dominant conduction mechanisms are nearest neighbor hopping and variable-range hopping through localized states. Our systematic study provides a coherent understanding of transport in gapped bilayer graphene.