Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 25: FS: Iron-Based Superconductors

TT 25.7: Talk

Wednesday, March 24, 2010, 17:15–17:30, H20

Energy and temperature dependence of spin fluctuations in electron-doped iron arsenide superconductors — •Dmytro Inosov¹, Jitae Park¹, Philippe Bourges², Dunlu Sun¹, Yvan Sidis², Astrid Schneidewind^3,4, Klaudia Hradil^4,5, Daniel Haug¹, Chengtian Lin¹, Bernhard Keimer¹, and Vladimir Hinkov¹ — ¹MPI für Festkörperforschung, Stuttgart, Germany — ²LLB, CEA-CNRS, CEA Saclay, France — ³Inst. für Festkörperphysik, TU Dresden, Germany — ⁴FRM-II, TU München, Garching, Germany — ⁵Institut für Physikalische Chemie, Univ. Göttingen, Germany

Using inelastic neutron scattering we have studied the spin excitations in optimally doped BaFe_1.85Co_0.15As₂ (T_c=25 K) over a wide range of temperatures and energies. We present the results in absolute units and find that the normal state spectrum carries a weight comparable to underdoped cuprates. In contrast to cuprates, however, the spectrum agrees well with predictions of the theory of nearly antiferromagnetic metals, without complications arising from a pseudogap or competing incommensurate spin-modulated phases. We also show that the temperature evolution of the resonance energy follows the superconducting energy gap, as expected from conventional Fermi-liquid approaches. Our observations point to a surprisingly simple theoretical description of the spin dynamics in the iron arsenides and provide a solid foundation for models of magnetically mediated superconductivity.