Image potential states as quantum probe of graphene interfaces

TL;DR

This paper experimentally confirms the existence of a double Rydberg series of image potential states in mono- and bilayer graphene, demonstrating their potential as quantum probes of interfacial coupling in graphene interfaces.

Contribution

It provides the first experimental validation of the double Rydberg series of IPSs in graphene and compares these states with ab-initio calculations, highlighting their role as probes of interfacial interactions.

Findings

Double Rydberg series of IPSs confirmed in graphene

IPSs persist despite substrate influence

IPSs evolve into a single series in graphite

Abstract

Image potential states (IPSs) are electronic states localized in front of a surface in a potential well formed by the surface projected bulk band gap on one side and the image potential barrier on the other. In the limit of a two-dimensional solid a double Rydberg series of IPSs has been predicted which is in contrast to a single series present in three-dimensional solids. Here, we confirm this prediction experimentally for mono- and bilayer graphene. The IPSs of epitaxial graphene on SiC are measured by scanning tunnelling spectroscopy and the results are compared to ab-initio band structure calculations. Despite the presence of the substrate, both calculations and experimental measurements show that the first pair of the double series of IPSs survives, and eventually evolves into a single series for graphite. Thus, IPSs provide an elegant quantum probe of the interfacial coupling in graphene systems.