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Electronic phase diagram of the LaO1-x Fx FeAs superconductor: A muon spin relaxation study

Hubertus Luetkens Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


In this talk I will review our muon spin relaxation (µSR) studies [1-6] on the recently discovered Fe-based superconductors. The focus will be laid on the structural and electronic phase diagram of LaO_1-x F_x FeAs 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, µSR and Mössbauer spectroscopy. Our experiments yield information on both, the doping dependence of the transition temperatures and the respective order parameters. In strong contrast to cuprates and heavy fermions we find a discontinuous first-order-like change of the Néel temperature, the superconducting transition temperature, the sublattice magnetisation and the superfluid density. 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 phase boundary between the magnetic SDW and the superconducting state.

 

[1] H. Luetkens, H.-H. Klauss, M. Kraken et al., Nature Materials (2009), DOI: 10.1038/NMAT2397

[2] H. Luetkens, H.-H. Klauss, R. Khasanov et al., Phys. Rev. Lett. 101, 097009 (2008)

[3] H.-H. Klauss, H. Luetkens, R. Klingeler et al., Phys. Rev. Lett. 101, 077005 (2008)

[4] A. Jesche, N. Caroca-Canales, H. Rosner et al., Phys. Rev. B 78, 180504(R) (2008)

[5] R. Khasanov, H. Luetkens, A. Amato et al., Phys. Rev. B 78, 092506 (2008)

[6] R. Khasanov, K. Conder, E. Pomjakushina et al., Phys. Rev. B 78, 220510 (2008)

 

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