Symmetry of standing waves generated by a point defect in epitaxial graphene

TL;DR

This study uses STM and FT-STM to analyze a point defect in epitaxial graphene, confirming Fermi liquid behavior and revealing anisotropic standing waves linked to electron chirality and sublattice asymmetry.

Contribution

First experimental verification of Fermi liquid theory in graphene over a wide energy range, with analysis of standing wave symmetry and defect-induced anisotropy.

Findings

Confirmation of Fermi liquid behavior in graphene

Observation of threefold anisotropy in standing waves

Relation between anisotropy, chirality, and sublattice asymmetry

Abstract

Using scanning tunneling microscopy (STM) and Fourier Transform STM (FT-STM), we have studied a point defect in an epitaxial graphene sample grown on silicon carbide substrate. This analysis allows us to extract the quasiparticle energy dispersion, and to give a first experimental proof of the validity of Fermi liquid theory in graphene for a wide range of energies from -800 meV to +800 meV. We also find evidence of a strong threefold anisotropy in the standing waves generated by the defect. We discuss possible relations between this anisotropy, the chirality of the electrons, and the asymmetry between graphene's two sublattices. All experimental measurements are compared and related to theoretical T-matrix calculations.