Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Superconductivity: Fe-based Superconductors - 122 Part 2 & Theory

TT 17.5: Talk

Tuesday, March 27, 2012, 10:45–11:00, H 2053

Magnetic Resonance from the Interplay of Frustration and Superconductivity — •Johannes Knolle¹, Ilya Eremin², Jorg Schmalian³, and Roderich Moessner¹ — ¹Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany — ²Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany — ³Karlsruhe Institute of Technology, Institute for Theory of Condensed Matter, D-76131 Karlsruhe, Germany

Motivated by iron-based superconductors, we develop a self-consistent electronic theory for the itinerant spin excitations in the regime of coexistence of the antiferromagnetic stripe order with wave vector Q₁=(π,0) and s± superconductivity. The onset of superconductivity leads to the appearance of a magnetic resonance near the wave vector Q₂=(0,π), where magnetic order is absent. This resonance is isotropic in spin space, unlike the excitations near Q₁, where the magnetic Goldstone mode resides. We discuss several features which can be observed experimentally. In particular, we find that the additional subtle effects of microscopic coexistence of AF and s± SC order, such as damping of the spin waves at Q₁ and the modified dispersing behavior of the spin resonance around Q₂, can be used by INS to distinguish the coexistence phenomenon from phase separation effects.