Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 39: SC: Iron-Based Superconductors - 1111
TT 39.8: Talk
Friday, March 26, 2010, 12:15–12:30, H19
Unusual disorder effects in La Fe As1−δ O0.9 F0.1 as revealed by NMR spectroscopy — •Franziska Hammerath1, Stefan-Ludwig Drechsler1, Hans-Joachim Grafe1, Guillaume Lang1, Günter Fuchs1, Günter Behr1, Ilya Eremin2, Maxim Korshunov2,3, and Bernd Büchner1 — 1Leibniz-Institut für Festkörper- & Werkstoffforschung, Dresden, Germany — 2MPI für Physik komplexer Systeme, Dresden — 3L.V. Kirensky Inst. of Physics, Sib. Branch of Russ. Acad. Scs., Krasnoyarsk, Russia
We report 75As NMR measurements of the spin-lattice relaxation in the superconducting state of LaFeAsO0.9F0.1 and As-deficient samples, LaFeAs1−δO0.9F0.1 with a drastic change of the 1/T1 temperature dependence below Tc from a T3-law for LaFeAsO0.9F0.1 to a Tβ-law (β=5−6) for LaFeAs1−δO0.9F0.1. Tc and the slope of the upper critical field near Tc increase unexpectedly in the As-deficient samples. Our results are discussed in terms of non-universal SC gaps in Fe-pnictides and the effect of As deficiency as an exotic case when nonmagnetic ’smart’ impurities even stabilize an s±−wave superconductor as well as within a scenario of a disorder driven change to conventional s++ superconductivity.
[1] H.-J. Grafe et al., Phys. Rev. Lett. 101, 047003 (2008).