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

TL;DR

This study reveals that in gated graphene, quantum Hall transport quantization occurs before the bulk Landau levels are fully filled, challenging traditional understanding of the relationship between bulk states and transport quantization.

Contribution

It provides new insights into the correlation between bulk Landau level filling and transport quantization in graphene, using combined transport and microwave impedance microscopy.

Findings

Quantized transport occurs below complete bulk Landau level filling.

Bulk remains conductive during transport quantization.

Implications for understanding quantum Hall effects in 2D systems.

Abstract

We report simultaneous transport and scanning microwave impedance microscopy to examine the correlation between transport quantization and filling of the bulk Landau levels in the quantum Hall regime in gated graphene devices. Surprisingly, a comparison of these measurements reveals that quantized transport typically occurs below the complete filling of bulk Landau levels, when the bulk is still conductive. This result points to a revised understanding of transport quantization when carriers are accumulated by gating. We discuss the implications on transport study of the quantum Hall effect in graphene and related topological states in other two-dimensional electron systems.