Disentangling the Complex Electronic Structure of an Adsorbed Nanographene: Cycloarene C108

TL;DR

This study uses advanced spectroscopy, functionalized tips, and data analysis to precisely characterize the electronic structure of a complex adsorbed nanographene molecule, revealing detailed molecular orbitals and close-lying states.

Contribution

It introduces a combined experimental and computational approach for detailed electronic structure analysis of complex molecules on surfaces.

Findings

Enhanced visibility of molecular resonances with CO tips

Excellent agreement between experiment and DFT calculations

Disentangling of molecular states separated by 50 meV

Abstract

We combine low-temperature scanning tunneling spectroscopy, CO functionalized tips and algorithmic data analysis to investigate the electronic structure of the molecular cycloarene C108 (graphene nanoring) adsorbed on a Au(111) surface. We demonstrate that CO functionalized tips enhance the visibility of molecular resonances, both in differential conductance spectra and in real-space topographic images without introducing spurious artifacts. Comparing our experimental data with ab-initio density functional theory reveals a remarkably precise agreement of the molecular orbitals and enables us to disentangle close-lying molecular states only separated by 50 meV at an energy of 2 eV below the Fermi level. We propose this combination of techniques as a promising new route for a precise characterization of complex molecules and other physical entities which have electronic resonances in the tip-sample junction.