Wave function mapping in graphene quantum dots with soft confinement

TL;DR

This study maps the wave functions of graphene quantum dots on Ir(111) using spectroscopy, revealing soft confinement effects and substrate interactions that influence their electronic properties and symmetry.

Contribution

It provides the first detailed wave function mapping of graphene quantum dots with soft-wall confinement on a substrate, combining experimental spectroscopy with theoretical modeling.

Findings

Wave functions exhibit high symmetry due to soft-wall confinement.

Substrate interactions induce a band gap and influence wave function shape.

Moiré potential and surface resonance penetration affect electronic properties.

Abstract

Using low-temperature scanning tunneling spectroscopy, we map the local density of states (LDOS) of graphene quantum dots supported on Ir(111). Due to a band gap in the projected Ir band structure around the graphene K point, the electronic properties of the QDs are dominantly graphene-like. Indeed, we compare the results favorably with tight binding calculations on the honeycomb lattice based on parameters derived from density functional theory. We find that the interaction with the substrate near the edge of the island gradually opens a gap in the Dirac cone, which implies soft-wall confinement. Interestingly, this confinement results in highly symmetric wave functions. Further influences of the substrate are given by the known moir{\'e} potential and a 10% penetration of an Ir surface resonance