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TT: Fachverband Tiefe Temperaturen

TT 5: Postersession Superconductivity: Materials - Fabrication and Properties

TT 5.2: Poster

Monday, March 23, 2009, 13:00–16:45, P1A

Superconducting properties of boron-doped diamond — •M. Uhlarz¹, R. Skrotzki¹, T. Papageorgiou¹, J. Wosnitza^1,2, N. Dubrovinskaia^3,4, L. Dubrovinsky⁵, N. Miyajima⁵, A. Bosak⁶, M. Krisch⁶, H.F. Braun⁷, and R. Wirth⁸ — ¹Hochfeld-Magnetlabor Dresden, Forschungszentrum Dresden-Rossendorf — ²Institut für Festkörperphysik, TU Dresden — ³Institut für Geowissenschaften, Universität Heidelberg — ⁴Lehrstuhl für Kristallographie, Physikalisches Institut, Universität Bayreuth — ⁵Bayerisches Geoinstitut, Universität Bayreuth — ⁶European Synchrotron Radiation Facility, Grenoble — ⁷Physikalisches Institut, Universität Bayreuth — ⁸GeoForschungsZentrum Potsdam

The question of the nature of superconductivity in boron-doped diamond (synthesized at high pressures and high temperatures) is still open. Here we present consistent measurements of resistivity and specific-heat on two samples containing pure ¹³C and ¹²C, revealing a 0.2 K shift of the superconducting transition temperature T_c. Hall-coefficient measurements confirm equal charge-carrier concentrations in both samples. The results are interpreted as a carbon-isotope effect more than two times larger than expected from the most simple BCS model for phonon-mediated superconductivity. Additional analyses of microstructure and exact boron content of the superconducting material show the presence of highly boron-enriched amorphous boundaries between the grains. For these investigations high-resolution transmission-electron microscopy and electron-energy-loss spectroscopy were used.