Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 79: Superconductivity: Fe-based Superconductors - 122

TT 79.1: Vortrag

Donnerstag, 10. März 2016, 15:30–15:45, H21

Magnetic Excitations in Na-doped BaFe₂As₂ — •Florian Waßer¹, Sabine Wurmehl², Saicharan Aswarthem², Yvan Sidis³, Astrid Schneidewind^4,5, Jitae Park⁵, Bernd Büchner², and Markus Braden¹ — ¹II. Physikalisches Institut, Universität zuKöln, Zülpicher Strasse 77, D-50937 Köln, Germany — ²Institute for Solid State Research, IFW Dresden,D-01171 Dresden, Germany — ³Laboratoire LéonBrillouin, CEA-CNRS, CEA Saclay, 91191 Gif-sr-Yvette Cedex,France — ⁴Jülich Centre for Neutron ScienceJCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ,D-85747, Garching, Germany — ⁵Forschungsneutronenquelle Heinz Maier-Leibnitz(FRM-II), TU München, D-85747 Garching, Germany

Our neutron scattering study of magnetic excitations in Ba_1−xNa_xFe₂As₂ show that the presence of static antiferromagnetic (AFM) order dominates the low-energy part of the spectrum even in the superconducting (SC) state. In the coexistence regime i.e. at 35% and 39% Na-doping an additional sharp and intense low-energy resonance mode, centred at ∼4meV, develops below T_c. This low-energy resonance excitation is predominantly polarized along the c-direction, which corresponds to a longitudinal alignment due to the spin-reorientation in this material. In the SC phase the elastic AFM signal becomes strongly reduced suggesting that the corresponding spectral weight is shifted to higher energies and in particular to the development of the 4meV-mode. In contrast, at 40% Na-doping static AFM order is absent and the 4meV-mode is fully suppressed.