Evidence for Pauli-limiting behaviour at high fields and enhanced upper critical fields near T_c in several disordered FeAs based Superconductors

G. Fuchs; S. -L. Drechsler; N. Kozlova; M. Bartkowiak; G. Behr; K. Nenkov; H. -H. Klauss; J. Freudenberger; M. Knupfer; F. Hammerath; G. Lang; H. -J. Grafe; B. Buechner; L. Schultz

doi:10.1016/j.physc.2009.10.086

arXiv · 0908.2101

Evidence for Pauli-limiting behaviour at high fields and enhanced upper critical fields near T_c in several disordered FeAs based Superconductors

G. Fuchs·S. -L. Drechsler·N. Kozlova·M. Bartkowiak·G. Behr·K. Nenkov·H. -H. Klauss·J. Freudenberger·M. Knupfer·F. Hammerath·G. Lang·H. -J. Grafe·B. Buechner·L. Schultz

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Abstract

We report resistivity and upper critical field B_c2(T) data for disordered (As deficient) LaO_0.9F_0.1FeAs_1-delta in a wide temperature and high field range up to 60 T. These samples exhibit a slightly enhanced superconducting transition at T_c = 28.5 K and a significantly enlarged slope dB_c2/dT = -5.4 T/K near T_c which contrasts with a flattening of B_c2(T) starting near 23 K above 30 T. The latter evidences Pauli limiting behaviour (PLB) with B_c2(0) approximately 63 T. We compare our results with B_c2(T)-data from the literature for clean and disordered samples. Whereas clean samples show almost no PLB for fields below 60 to 70 T, the hitherto unexplained pronounced flattening of B_c2(T) for applied fields H II ab observed for several disordered closely related systems is interpreted also as a manifestation of PLB. Consequences are discussed in terms of disorder effects within the frames of (un)conventional superconductivity, respectively.

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G. Fuchs, S. -L. Drechsler, N. Kozlova, M. Bartkowiak, G. Behr, K. Nenkov, H. -H. Klauss, J. Freudenberger, M. Knupfer, F. Hammerath, G. Lang, H. -J. Grafe, B. Buechner, L. Schultz. 2009-08-14. Evidence for Pauli-limiting behaviour at high fields and enhanced upper critical fields near T_c in several disordered FeAs based Superconductors. https://doi.org/10.1016/j.physc.2009.10.086

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