•H. Rosner1, S.-L. Drechsler2, G. Fuchs2,
K.-H. Müller2, G. Behr2, H. Eschrig2,
R. Heid3, E. Forzani4, K. Winzer4, Y.
Naidyuk5 und 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 l 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.