Gate-tunable acoustoelectric effect in graphene

We demonstrate in situ gate-tunable acoustoelectric transport in exfoliated monolayer graphene by measuring the voltage created as high-frequency surface acoustic waves dynamically drive charge carriers in the graphene. We employ a flip-chip device configuration to conduct acoustoelectric measurements while simultaneously controlling the graphene carrier density with a metal-oxide back-gate. At high carrier density we observe dependence of the acoustoelectric signal on the sign of the graphene charge carriers, while at low densities we observe anomalous sign reversals of the acoustoelectrically generated voltage. We attribute these anomalous sign reversals to spatially heterogeneous conduction in the vicinity of charge neutrality.