Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 29: Symposium: Surface Spectroscopy on Kondo Systems I (Invited Speakers: Wolf-Dieter Schneider, Fakher Assaad, Serguei Molodtsov)
O 29.6: Vortrag
Dienstag, 26. Februar 2008, 13:15–13:30, HE 101
FeSi - Kondo insulator or itinerant system? — •Dirk Menzel1, Markus Klein2, Damian Zur1, Klaus Doll3, Friedrich Reinert2, and Joachim Schoenes1 — 1Technische Universität Braunschweig, Institut für Physik der Kondensierten Materie — 2Universität Würzburg, Lehrstuhl für Experimentelle Physik II — 3Max-Planck-Institut für Festkörperforschung, Stuttgart
The claim that FeSi is the first Kondo insulator containing no f-electrons [1] resulted in an intense discussion about the nature of this material. However, recent theoretical and experimental investigations have generated more and more arguments for an interpretation of apparently uncommon electronic properties in an itinerant band model. We have performed angle-resolved high-resolution photoemission spectroscopy on FeSi single crystals using a He spectral lamp as well as synchrotron radiation. The photoemission spectra agree qualitatively with the bandstructure derived from single-particle GGA calculations. However, we could also observe strong renormalization effects near the valence band maximum. A quantitative consistency can be obtained when an interaction among the Fe-d-electrons is added to the calculations in the form of self energy corrections. The resulting spectral function is in surprisingly good accordance to the experimental data. These results support the interpretation of FeSi as an itinerant material with d-correlations without the necessity of including Kondo interactions.
[1] G. Aeppli and Z. Fisk, Comments Cond. Mat. Phys. 16, 155 (1992).