Unconventional Correlation between Quantum Hall Transport Quantization and Bulk State Filling in Gated Graphene Devices

摘要

We report simultaneous transport and scanning microwave impedance microscopyto examine the correlation between transport quantization and filling of thebulk Landau levels in the quantum Hall regime in gated graphene devices.Surprisingly, a comparison of these measurements reveals that quantizedtransport typically occurs below the complete filling of bulk Landau levels,when the bulk is still conductive. This result points to a revisedunderstanding of transport quantization when carriers are accumulated bygating. We discuss the implications on transport study of the quantum Halleffect in graphene and related topological states in other two-dimensionalelectron systems.