Local Compressibility Measurements of Correlated States in Suspended Bilayer Graphene

TL;DR

This study uses local compressibility measurements to explore correlated electronic states in suspended bilayer graphene, revealing zero-field ordered states and field-dependent energy gaps indicative of strong Coulomb interactions.

Contribution

It provides direct local measurements of energy gaps and identifies potential ordered phases in bilayer graphene, advancing understanding of many-body effects in this material.

Findings

Zero-field incompressible region near charge neutrality

Energy gaps at v=0,1,2 scale linearly with magnetic field

Evidence of strong Coulomb interactions affecting electronic states

Abstract

Bilayer graphene has attracted considerable interest due to the important role played by many-body effects, particularly at low energies. Here we report local compressibility measurements of a suspended graphene bilayer. We find that the energy gaps at filling factors v = 4 do not vanish at low fields, but instead merge into an incompressible region near the charge neutrality point at zero electric and magnetic field. These results indicate the existence of a zero-field ordered state and are consistent with the formation of either an anomalous quantum Hall state or a nematic phase with broken rotational symmetry. At higher fields, we measure the intrinsic energy gaps of broken-symmetry states at v = 0, 1 and 2, and find that they scale linearly with magnetic field, yet another manifestation of the strong Coulomb interactions in bilayer graphene.