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TT: Fachverband Tiefe Temperaturen

TT 5: Postersession Superconductivity: Materials - Fabrication and Properties

TT 5.34: Poster

Monday, March 23, 2009, 13:00–16:45, P1A

Electronic phase diagram of the LaO_1−xF_xFeAs superconductor: A muon spin relaxation study — •H. Luetkens¹, H.-H. Klauss², F.J. Litterst³, T. Dellmann³, R. Klingeler⁴, C. Hess⁴, R. Khasanov¹, A. Amato¹, C. Baines¹, M. Kosmala⁵, O.J. Schumann⁵, M. Braden⁵, J. Hamann-Borrero⁴, N. Leps⁴, A. Kondrat⁴, G. Behr⁴, J. Werner⁴, and B. Büchner⁴ — ¹Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland — ²Institut für Festkörperphysik, TU Dresden — ³Institut für Physik der Kondensierten Materie, TU Braunschweig — ⁴Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden — ⁵II. Physikalisches Institut, Universität zu Köln

The structural and electronic phase diagram of LaO_1−xF_xFeAs and, in particular, the exact nature of the change from the magnetically ordered to the superconducting state that was determined by means of x-ray scattering, muSR and Mössbauer spectroscopy will be presented [1-3]. A discontinuous first-order-like change of the Néel temperature, the superconducting transition temperature, the sublattice magnetisation and the superfluid density is found between x=0.04 and x=0.05. While these results strongly question the relevance of quantum critical behaviour in iron pnictides they prove an important role of the structural orthorhombic distortion disappearing exactly at the SDW magnetism and superconductivity phase boundary.

[1] H. Luetkens et al., Phys. Rev. Lett. 101, 097009 (2008).

[2] H.-H. Klauss et al., Phys. Rev. Lett. 101, 077005 (2008).

[3] H. Luetkens et al., arXiv:0806.3533 (2008).