Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity - Poster Session

TT 8.14: Poster

Montag, 26. März 2007, 14:00–17:45, Poster A

Superconducting critical temperature and Fermi surface of hydrated cobalt compounds — •Jose Roberto Iglesias, Christopher Thomas, and Acirete Simoes — Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

We study the properties of some hydrated superconducting cobalt compounds of the type of Na_xCoO₂ · y(H₂O) in the superconducting phase. These compounds consist of CoO₂ layers separated by Na ions and water molecules, resulting in a Co triangular lattice. The theoretical approach here considered is an extended Hubbard model and we obtain the normal and anomalous Green functions of the system limit using mean field approximation for the inter-atomic interactions and Hubbard-I approximation for the intra-atomic ones. We consider the paramagnetic case and we analyze the coupling between electrons with different symmetries, so obtaining the singlet and triplet superconducting order parameters. The superconducting transition temperatures, T_c, are obtained in both cases. The doping dependence of T_c obtained for the triplet case is in a qualitative agreement with experimental results. Finally the Fermi surface is also calculated and compared with ARPES results.