Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 9: Supraleitung: Eigenschaften, elektronische Struktur, Ordnungsparameter

TT 9.6: Vortrag

Dienstag, 9. März 2004, 11:00–11:15, H20

Electronic structure and aspects of unconventional superconductivity in Na_xCoO₂ ^. yH₂O — •S.-L. Drechsler¹, H. Rosner², G. Fuchs¹, A. Wälte¹, G. Krabbes¹, K.-H. Müller¹, H. Eschrig¹, and A. Handstein¹ — ¹IFW-Dresden, D-01171, P.O. Box 270116, Dresden, Germany — ²MPI-CPfS Dresden, Germany

We examine the electronic structure of Na_xCoO₂ ^. yH₂O within the local density approximation. The parametrization of the band which forms the largest hole-Fermi surface centered at Γ shows significant deviations from what is frequently assumed in recent sophisticated theoretical studies. In particular, the commonly used nearest neighbor approaches in the framework of single band pictures are found to be unrealistic. The special role of H₂O in screening the disorder in the charge reservoir is briefly discussed and compared with the case of Y_1−xCa_xCu₃O_6+δ. We report strucural, magnetic susceptibility, and specific heat measurements of the unhydrated nonsuperconducting compounds. The results are compared with our findings for the superconducting perovskite MgCNi₃ which is close to a ferromagnetic instability.