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TT: Fachverband Tiefe Temperaturen

TT 45: Superconductivity: Fe-based Superconductors - 1111,111, FeSe

TT 45.5: Vortrag

Dienstag, 1. April 2014, 15:00–15:15, HSZ 201

Incommensurate antiferromagnetic fluctuations in superconducting LiFeAs — •Navid Qureshi¹, Paul Steffens², Daniel Lamago^3,4, Yvan Sidis³, Oleg Sobolev⁵, Russell Ewings⁶, Luminita Harnagea⁷, Sabine Wurmehl⁷, Bernd Büchner⁷, and Markus Braden¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Institut Laue Langevin, Grenoble — ³Laboratoire Léon Brillouin, C.E.A. Saclay — ⁴Institut für Festkörperphysik, Karlsruhe — ⁵Technische Universität München, FRM-II — ⁶ISIS Facility, Rutherford Appleton Laboratory, Didcot — ⁷Institut für Festkörper- und Werkstoffforschung, Dresden

We present an inelastic neutron scattering study on single-crystalline LiFeAs devoted to the characterization of the previously reported incommensurate antiferromagnetic fluctuations [1]. Time-of-flight measurements show their presence up to an energy transfer of 60 meV, while polarized neutrons in combination with longitudinal polarization analysis on a triple-axis spectrometer prove the pure magnetic origin of this signal. The normalization of the scattered intensity to an absolute scale yields that the magnetic fluctuations in LiFeAs are by a factor 8 weaker than in nearly optimally Co-doped BaFe₂As₂, although a factor 2 is recovered due to the incommensurability. The longitudinal polarization analysis gives hints for a weak spin-space anisotropy with slightly stronger out-of-plane component between 6 and 14 meV. Furthermore, our data suggest a fine structure of the magnetic signal most likely arising from two nesting vectors.
N. Qureshi et al., Phys. Rev. Lett 108 117001 (2012)