Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 17: SC: Iron-Based Superconductors - Theoretical Approaches
TT 17.6: Hauptvortrag
Dienstag, 23. März 2010, 15:30–16:00, H20
Nature of Pairing in the FeAs Superconductors — •Siegfried Graser1, Thomas A. Maier2, Alexander F. Kemper3, Peter J. Hirschfeld3, and Douglas J. Scalapino4 — 1Center for Electronic Correlations and Magnetism, University of Augsburg, Germany — 2Oak Ridge National Laboratory, Oak Ridge, USA — 3University of Florida, Gainesville, USA — 4University of California, Santa Barbara, USA
A comparison of the new high-Tc superconductors of the iron pnictide and chalcogenide family to the cuprates reveals startling similarities between the two classes: both are layered materials with mainly 2D character, a conductivity that is dominated by d-electrons, and an antiferromagnetic or spin-density wave phase in proximity to the superconducting state. However, the pronounced multiband character of the iron pnictides, that becomes manifest in several disconnected Fermi surface sheets, distinguishes them from the cuprates and requires a multiorbital description of its electronic properties. This multiorbital character of the bands at the Fermi level together with the rich momentum structure of the Fermi surface allows for a wide variety of possible superconducting ground states. We have explored the symmetry of the superconducting state assuming a pairing mechanism based on the exchange of spin fluctuations using a 5-orbital tight-binding Hamiltonian fitted to the LDA band structure of LaOFeAs. We could show that not only the symmetry but also the anisotropy of the pairing state depends sensitively on the intra- and interorbital interaction parameters.