Transport in gapped bilayer graphene: The role of potential fluctuations

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, R-NP(T), from 220 to 1.5 K. Above 5 K, R-NP(T) is dominated by two thermally activated processes in different temperature regimes and exhibits exp(T-3/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.