Graphene quantum dots in perpendicular magnetic fields

TL;DR

This study investigates the electronic properties of graphene quantum dots under perpendicular magnetic fields, revealing how their excited states and electron-hole crossover evolve with magnetic field strength.

Contribution

It provides detailed experimental insights into the magnetic field dependence of excited states and Landau level formation in graphene quantum dots near charge neutrality.

Findings

Observation of Coulomb blockade resonances across the transport gap.

Identification of the E=0 Landau level formation in the magnetic spectrum.

Detailed mapping of excited state evolution with magnetic field.

Abstract

We report transport experiments on graphene quantum dots. We focus on excited state spectra in the near vicinity of the charge neutrality point and signatures of the electron-hole crossover as a function of a perpendicular magnetic field. Coulomb blockade resonances of a 50 nm wide and 80 nm long dot are visible at all gate voltages across the transport gap ranging from hole to electron transport. The magnetic field dependence of more than 40 states as a function of the back gate voltage can be interpreted in terms of the unique evolution of the diamagnetic spectrum of a graphene dot including the formation of the E = 0 Landau level, situated in the center of the transport gap, and marking the electron-hole crossover.