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TT: Fachverband Tiefe Temperaturen

TT 45: Superconductivity: Ferropnictides 2

TT 45.6: Talk

Friday, March 27, 2009, 11:45–12:00, HSZ 03

Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors. — •Dmitri Efremov¹, Ilya Eremin², and Andrey Chubukov³ — ¹TU Dresden — ²MPIPKS Dresden — ³Universtity of Wisconsin

We analyze antiferromagnetism and superconductivity in novel Fe−based superconductors within the itinerant model of small electron and hole pockets near (0,0) and (π,π). We argue that the effective interactions in both channels logarithmically flow towards the same values at low energies, i.e., antiferromagnetism and superconductivity must be treated on equal footings. The magnetic instability comes first for equal sizes of the two pockets, but looses to superconductivity upon doping. The superconducting gap has no nodes, but changes sign between the two Fermi surfaces (extended s-wave symmetry). We argue that the T dependencies of the spin susceptibility and NMR relaxation rate for such state are exponential only at very low T, and can be well fitted by power-laws over a wide T range below T_c.