Details

Autor(en) / Beteiligte

• Luetkens, H.
• Klauss, H.-H.
• Kraken, M.
• Litterst, F. J.
• Dellmann, T.
• Klingeler, R.
• Hess, C.
• Khasanov, R.
• Amato, A.
• Baines, C.
• Kosmala, M.
• Schumann, O. J.
• Braden, M.
• Hamann-Borrero, J.
• Leps, N.
• Kondrat, A.
• Behr, G.
• Werner, J.
• Büchner, B.

Titel

The electronic phase diagram of the LaO1−xFxFeAs superconductor

Ist Teil von

• Nature materials, 2009-04, Vol.8 (4), p.305-309

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2009

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• In non-conventional superconductors, it is usually found that superconductivity emerges in the vicinity of a critical point where antiferromagnetic order gradually disappears—corresponding to a second-order transition. Investigation of the newly discovered iron pnictide superconductors challenges this picture, showing an abrupt, first-order transition. The competition of magnetic order and superconductivity is a key element in the physics of all unconventional superconductors, for example in high-transition-temperature cuprates 1 , heavy fermions 2 and organic superconductors 3 . 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 superconductors 4 , 5 , 6 . Similar to other unconventional superconductors, the parent compounds of the pnictides show a magnetic ground state 7 , 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 LaO 1− x F x FeAs. 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.