Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 92: Superconductivity: Fe-based Superconductors - Theory II
TT 92.5: Vortrag
Donnerstag, 3. April 2014, 16:00–16:15, HSZ 201
Spin fluctuations and superconductivity in KxFe2−ySe2 — •Andreas Kreisel1, Yan Wang1, Thomas A. Maier2, Peter J. Hirschfeld1, and Douglas J. Scalapino3 — 1Department of Physics, University of Florida, USA — 2Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, USA — 3Department of Physics, University of California, USA
Superconductivity in alkali-intercalated iron selenide, with Tc’s of 30 K and above, may have a different origin than that of the other Fe-based superconductors, since the Fermi surface seems not to have any sheets centered around the Γ point. Here we investigate the symmetry of the superconducting gap in the framework of spin-fluctuation pairing calculations using DFT bands downfolded onto a 3D, ten-orbital tight-binding model, treating the interactions in the random-phase approximation. We find a leading instability towards a state with d-wave symmetry, but show that the details of the gap function depend sensitively on electronic structure. The crystal symmetry requires quasi-nodes to occur, which are either horizontal, looplike or vertical depending on details. We investigate the possibility that spin-orbit coupling effects on the one-electron band structure, which lead to enhanced splitting of the two M-centered electron pockets in the 2-Fe zone, may stabilize the bonding-antibonding s±-wave states. Finally, we discuss our results in the context of current phenomenological theories and experiments and address the question of the origin of the spin-resonance that has been observed in inelastic neutron scattering experiments.