Letter abstract

Nature Materials 8, 305 - 309 (2009)
Published online: 22 February 2009 | doi:10.1038/nmat2397

Subject Categories: Electronic materials | Superconductors

The electronic phase diagram of the LaO1-xFxFeAs superconductor

H. Luetkens1, H.-H. Klauss2, M. Kraken3, F. J. Litterst3, T. Dellmann2,3, 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 & B. Büchner4


The competition of magnetic order and superconductivity is a key element in the physics of all unconventional superconductors, for example in high-transition-temperature cuprates1, heavy fermions2 and organic superconductors3. Here superconductivity is often found close to a quantum critical point where long-range antiferromagnetic order is gradually suppressed as a function of a control parameter, for example charge-carrier doping or pressure. It is believed that dynamic spin fluctuations associated with this quantum critical behaviour are crucial for the mechanism of superconductivity. Recently, high-temperature superconductivity has been discovered in iron pnictides, providing a new class of unconventional superconductors4, 5, 6. Similar to other unconventional superconductors, the parent compounds of the pnictides show a magnetic ground state7, 8 and superconductivity is induced on charge-carrier doping. In this Letter the structural and electronic phase diagram is investigated by means of X-ray scattering, muon spin relaxation and Mössbauer spectroscopy on the series LaO1-xFxFeAs. We find a discontinuous first-order-like change of the Néel temperature, the superconducting transition temperature and the respective order parameters. Our results strongly question the relevance of quantum critical behaviour in iron pnictides and prove a strong coupling of the structural orthorhombic distortion and the magnetic order both disappearing at the phase boundary to the superconducting state.

  1. Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
  2. Institut für Festkörperphysik, TU Dresden, D-01069 Dresden, Germany
  3. Institut für Physik der Kondensierten Materie, TU Braunschweig, D-38106 Braunschweig, Germany
  4. Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, D-01171 Dresden, German
  5. II. Phyikalisches Institut, Universität zu, Köln D-50937, Germany

Correspondence to: H.-H. Klauss2 e-mail: h.klauss@physik.tu-dresden.de


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