Electron-Hole Crossover in Graphene Quantum Dots

TL;DR

This study explores the electron-hole crossover in a graphene quantum dot by analyzing its addition spectrum and magnetic field dependence, revealing complex diamagnetic behavior and excited state spectra near charge neutrality.

Contribution

It provides detailed experimental insights into the magnetic field evolution of the energy spectrum in graphene quantum dots during the electron-hole crossover, highlighting unique diamagnetic and Landau level features.

Findings

Coulomb blockade resonances observed across the transport gap.

Complex evolution of the diamagnetic spectrum from low to high magnetic fields.

Rich excited state spectrum near charge neutrality.

Abstract

We investigate the addition spectrum of a graphene quantum dot in the vicinity of the electron-hole crossover as a function of perpendicular magnetic field. Coulomb blockade resonances of the 50 nm wide dot are visible at all gate voltages across the transport gap ranging from hole to electron transport. The magnetic field dependence of more than 50 states displays the unique complex evolution of the diamagnetic spectrum of a graphene dot from the low-field regime to the Landau regime with the n=0 Landau level situated in the center of the transport gap marking the electron-hole crossover. The average peak spacing in the energy region around the crossover decreases with increasing magnetic field. In the vicinity of the charge neutrality point we observe a well resolved and rich excited state spectrum.