Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 18: Superconductivity: Borides, Borocarbides, Carbides, ...
TT 18.5: Vortrag
Dienstag, 28. März 2006, 16:00–16:15, HSZ 02
Superconducting properties of the 13 K rare earth carbide superconductor, La2C3 — •Jun Sung Kim, Reinhard K. Kremer, Volodymyr Babizhetskyy, Ove Jepsen, and Arndt Simon — MPI-FKF, 70569 Stuttgart
Superconductivity in rare earth carbides has attracted interest again after the recent discovery of the 18 K superconductor Y2C3.[1] We have successfully synthesized the related La system, La2C3, and after a careful control of the carbon content and the annealing procedures, optimized the superconducting properties reaching at sharp transition temperature Tc ∼ 13.2 K. The superconducting properties have been investigated by heat capacity measurements in magnetic fields up to H= 9 T, resistivity and magnetization measurements up to H = 30 T. The characteristic specific heat anomaly is compared to the predictions of the BCS and the α model, and a quantitative estimate of the electron-phonon coupling strength and the logarithmic average phonon frequency is made. From a detailed analysis including full potential electronic structure calculations based on the refined structure gained from the refinement of low-temperature neutron powder diffraction experiments, La2C3 is found to be in the strong electron-phonon coupling regime. The upper critical fields show a clear enhancement with respect to the Werthamer-Helfand-Hohenberg prediction and amount to ∼ 20 T at 0 K.
[1] G. Amano, S. Akutagawa, T. Muranaka, Y. Zenitani, and J. Akimutsu, J. Phys. Soc. Jpn. 73, 530 (2004).