Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 36: Focussed Session: Superconductivity and Magnetism in Ferropnictides and Related Materials

TT 36.2: Hauptvortrag

Donnerstag, 26. März 2009, 10:00–10:30, HSZ 03

Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors — •Andrey Chubukov — Dept . of Physics, University of Wisconsin, 1150 University ave., Madison WI 53706

I discuss the interplay between antiferromagnetism and superconductivity in novel Fe-based superconductors within the itinerant model of small electron and hole pockets. I argue that the effective interactions in both magnetic and pairing channels logarithmically flow towards the same values at low energies, i.e., antiferromagnetism and superconductivity are competing orders. The magnetic instability comes first for equal sizes of hole and electron pockets, but looses to superconductivity upon doping. I discuss the transition between the two ordered states and argue that it must be first order. The superconducting gap has no nodes, but changes sign between the two Fermi surfaces (extended s-wave symmetry). I discuss properties of such superconductors and the effects of non-magnetic impurities. I argue that the temperature dependencies of the spin susceptibility, the NMR relaxation rate and the superfluid density are exponential for the clean case, but become power-laws in the dirty limit. I discuss potential smoking-gun experiments to probe extended s-wave symmetry.