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Mattias L. N. Palsgaard: First Principles Simulations of Inelastic Tunnel Spectroscopy on Graphene

posted 12 Aug 2014, 00:16 by Lisbeth Kirk Mynster
Mattias L N Palsgaard, Center for Nanostructured Graphene, Dept. of Micro- and Nanotechnology, Technical University of Denmark, Ørsted Plads, Bldg. 345E, DK-2800 Kongens Lyngby, Denmark. 
Inelastic tunneling into a suspended graphene sheet is investigated, using Density Functional Theory combined with the Non-Equilibrium Green’s Function formalism. Electronic coupling to the vibrations in graphene is included, with a Lowest Order Expansion of the Self-Consistent Born Approximation.The results show a gap in tunneling conductance unique to graphene and caused by inelastic effects. The physics of this phenomenon is captured approximately by the method used. The gap is independent on change in the gate voltage and increase of the tunneling distance. The stability of the gap feature, with respect to various modifications of the pristine graphene lattice, is tested.Imperfections in the graphene lattice are found to quench the gap locally, leading to artificial protrusions in STM topography images. Additionally, inelastic fingerprints are found for a range of different imperfections ranging from structural defects to covalently bonded adsorbates and edges. 
Mattias Palsgaard graduated from the Technical University of Denmark (DTU) in March 2014 as a Civil Engineer in Physics and Nanotechnology.
He has since then been working as a Research Assistant in the group of Assoc. Prof. Mads Brandbyge at DTU. His main focus is on first principles calculation of Scanning Tunneling Microscopy measurements on grapheme including electron coupling to vibrations of the crystal lattice. In July of 2014, he received the Best Poster Award at the Quantumhagen Conference in Copenhagen.