Longitudinal and transverse frictional drag in graphene/ LaAlO3/SrTiO3 heterostructures

Heterostructures composed of different layered materials provide novel opportunities to investigate the electronic correlations between them. Here we investigate frictional drag between graphene and LaAlO3/SrTiO3 (LAO/STO) heterostructures. The LAO/STO layer underneath the graphene is rendered conductive using conductive atomic force microscope (c-AFM) lithography, creating a two-layer system in which the LAO serves as an ultrathin (<2 nm) insulating barrier. By sourcing current in both the STO layer and graphene layer, Coulomb drag is studied in a wide range, from an STO superconducting region to a graphene quantum Hall region. Pronounced fluctuations in the frictional drag resistance are observed when the STO is superconducting. A large enhancement of drag resistance is observed when the STO becomes superconducting. Pronounced stripelike oscillations in the frictional drag appear in the quantum Hall region, both along the main channel and the transverse (Hall) configuration. The behavior is consistent with numerical simulations that model energy and momentum transfer from the STO layer to the graphene layer. These help to create a platform for graphene-based metamaterials using the programmable LAO/STO interface.