Giant-Capacitance-Induced Wide Quantum Hall Plateaus in Graphene on LaAlO_3/SrTiO_3 Heterostructures

Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities. We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO_3/SrTiO_3 heterostructures. Well-defined quantized Hall resistance plateaus at filling factors v=\pm2 can be obtained over wide ranges of the magnetic field and gate voltage, e.g., extending from 2 T to a maximum available magnetic field of 9 T. By using a simple band diagram model, it is revealed that these wide plateaus arise from the ultra-large capacitance of the ultra-thin LAO layer acting as the dielectric layer. This is distinctly different from the case of epitaxial graphene on SiC substrates, where the realization of giant Hall plateaus relies on the charge transfer between the graphene layer and interface states in SiC. Our results offer an alternative route towards optimizing the quantum Hall performance of graphene, which may find its applications in the further development of quantum resistance metrology.