Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 11: C/diamond

HL 11.1: Vortrag

Montag, 25. Februar 2008, 11:00–11:15, EW 202

Discontinuity of the loss function at large momentum transfers in graphite. — •Ralf Hambach^1,2, Christine Giorgetti¹, Frank Ortmann², Karsten Hannewald², Francesco Sottile¹, Apostolos G. Marinopoulos³, Friedhelm Bechstedt², and Lucia Reining¹ — ¹Laboratoire des Solides Irradiés, CEA-CNRS UMR 7642-Ecole Polytechnique, 91128 Palaiseau Cedex, France and European Theoretical Spectroscopy Facility (ETSF), Palaiseau, France — ²IFTO, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany — ³Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA

The loss function of graphite was studied for momentum transfers q beyond the first Brillouin zone. Surprisingly, near Bragg reflexes, the spectra are highly dependent upon very small changes in q, which reminds the non-analyticity of the loss function in the optical limit (q→ 0). The effect is investigated by means of first principle calculations within the random phase approximation (RPA). We find crystal local field effects to be crucial and propose a simple 2×2 model dielectric function.