Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 8: Postersitzung I: Supraleitung

TT 8.46: Poster

Monday, March 8, 2004, 14:30–19:00, Poster A

Superconductivity and weak electron-phonon coupling in transition metal diborides — •H. Rosner¹, S.-L. Drechsler², G. Fuchs², K.-H. Müller², G. Behr², H. Eschrig², R. Heid³, E. Forzani⁴, K. Winzer⁴, Y. Naidyuk⁵, and O. Otani⁶ — ¹Max Planck Institut für Chemische Physik fester Stoffe — ²Institut für Festkörper und Werkstoffforschung Dresden — ³FZ Karlsruhe — ⁴Universität Göttingen — ⁵NAS Kharkiv, Ukraine — ⁶NIMS Tsukuba, Japan

After the surprising discovery of superconductivity at 40K in MgB₂ an intense search for other superconducting diborides was started. Several contradicting reports about the superconductivity in TB₂ (T = transition metal) have been published so far, and the discussion is not settled yet. Combining extensive electronic structure and model calculations with various experiments (specific heat, resistivity, susceptibility, de-Haas-van-Alphen oscillations, point contacts) we investigate the electronic structure and the electron-phonon coupling λ in various TB₂ with focus on ZrB₂. Based on our calculations, we provide a clear microscopic picture for the rather weak electron-phonon coupling in these systems and the absence of conventional superconductivity in agreement with the empirically determined values from thermodynamic and transport measurements. Open problems are briefly discussed.