Quantum capacitance and density of states of graphene

TL;DR

This study measures the quantum capacitance of graphene to understand its density of states near the charge neutrality point, revealing significant fluctuations consistent with potential disorder.

Contribution

It provides experimental data on quantum capacitance in graphene using a resonant LC circuit, highlighting the impact of potential fluctuations on the density of states.

Findings

Quantum capacitance is significantly above zero near neutrality point.

Density of states is affected by potential fluctuations of about 100 meV.

Results agree with scanning single-electron transistor and nanoribbon studies.

Abstract

We report on measurements of the quantum capacitance in graphene as a function of charge carrier density. A resonant LC-circuit giving high sensitivity to small capacitance changes is employed. The density of states, which is directly proportional to the quantum capacitance, is found to be significantly larger than zero at and around the charge neutrality point. This finding is interpreted to be a result of potential fluctuations with amplitudes of the order of 100 meV in good agreement with scanning single-electron transistor measurements on bulk graphene and transport studies on nanoribbons.