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

Using scanning tunneling microscopy (STM) and Fourier Transform STM (FT-STM), we have studied a point defect in epitaxial graphene grown on silicon carbide substrate. We find a strong threefold anisotropy in the standing waves generated by the defect. We discuss possible relations between this anisotropy and the chirality of the electrons, and how it allows us to identify the position of the impurity. We extract the quasiparticle energy dispersion, and 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. All experimental measurements are compared and related to theoretical T-matrix calculations.