Probing Charging and Localization in the Quantum Hall Regime by Graphene pnp Junctions

TL;DR

This study investigates conductance fluctuations in high-quality graphene pnp junctions within the quantum Hall regime, revealing Coulomb-induced charging effects and the significance of electronic interactions in localized states.

Contribution

We demonstrate that conductance fluctuations in graphene pnp junctions are caused by Coulomb charging of localized states, highlighting the role of electron interactions in the quantum Hall regime.

Findings

Conductance fluctuations form crisscrossing lines parallel to QH plateaus.

Fluctuations exhibit different temperature dependences for peaks and valleys.

Charging of localized states influences conductance in the delocalized bulk.

Abstract

Using high quality graphene pnp junctions, we observe prominent conductance fluctuations on transitions between quantum Hall (QH) plateaus as the top gate voltage Vtg is varied. In the Vtg-B plane, the fluctuations form crisscrossing lines that are parallel to those of the adjacent plateaus, with different temperature dependences for the conductance peaks and valleys. These fluctuations arise from Coulomb-induced charging of electron- or hole-doped localized states when the device bulk is delocalized, underscoring the importance of electronic interactions in graphene in the QH regime.