Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 52: Methods: Atomic and Electronic Structure II

O 52.4: Talk

Thursday, March 29, 2007, 12:00–12:15, H42

Electron coincidence spectroscopy from surfaces: insulator vs. metal — •Frank Oliver Schumann, Carsten Winkler, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik

The effect of electron correlation manifests itself in the creation of the exchange-correlation (xc) hole. This theoretical concept is an important part of modern solid state theory. We have shown previously that the xc-hole is experimentally accessible via electron pair emission from surfaces. In order to assure that the xc-hole can be fully mapped we devised a new time-of-flight set-up with large angular acceptance. This is achieved by means of three channelplate detectors with delay lines anodes. We demonstrate that the xc-hole can now be fully mapped and a material dependent study becomes feasible. This is of general interest for a deeper understanding of the electron-electron interaction. We report on the first experiment aiming to unravel the material dependence of the xc-hole. We compare a Cu(100) surface with an insulator like LiF(100) and find distinctive differences in the electron-electron interaction. The spatial extension of the xc-hole shows a larger size for Cu compared to LiF. We further find that the angular extension of the xc-hole is indepedent of the kinetic energy in both cases. For certain energies of the electrons the xc-hole vanishes. The origin of this behavior is connected to the 2D-energy distributions.