# Impurity scattering and size quantization effects in a single graphene nanoflake

## TL;DR

This study uses Fourier-transform scanning tunneling spectroscopy and tight-binding calculations to analyze impurity scattering and size quantization effects in a graphene nanoflake, revealing insights into its electronic spectrum and quasiparticle interactions.

## Contribution

It provides a detailed experimental and theoretical analysis of impurity scattering and size quantization in a graphene nanoflake, highlighting the role of transverse modes and defect-induced pseudospin breaking.

## Key findings

- Interference patterns relate to scattering between transverse modes.
- Quasiparticle lifetime is significantly reduced due to substrate interactions.
- Flower defects enable intravalley back-scattering by breaking pseudospin symmetry.

## Abstract

By using Fourier-transform scanning tunneling spectroscopy we measure the interference patterns produced by the impurity scattering of confined Dirac quasiparticles in epitaxial graphene nanoflakes. Upon comparison of the experimental results with tight-binding calculations of realistic model flakes, we show that the characteristic features observed in the Fourier-transformed local density of states are related to scattering between different transverse modes (sub-bands) of a graphene nanoflake and allow direct insight into the electronic spectrum of graphene. We also observe a strong reduction of quasiparticle lifetime which is attributed to the interaction with the underlying substrate. In addition, we show that the distribution of the onsite energies at flower defects leads to an effectively broken pseudospin selection rule, where intravalley back-scattering is allowed.