Upper critical field measurements up to 60 T in arsenic-deficient LaO_(0.9)F_(0.1)FeAs_(1-delta): Pauli limiting behaviour at high fields vs improved superconductivity at low fields

G. Fuchs; S. -L. Drechsler; N. Kozlova; J. Freudenberger; M. Bartkowiak; J. Wosnitza; G. Behr; K. Nenkov; B. Buechner; L. Schultz

doi:10.1007/s10909-009-0145-z

arXiv · 0905.4917

Upper critical field measurements up to 60 T in arsenic-deficient LaO_(0.9)F_(0.1)FeAs_(1-delta): Pauli limiting behaviour at high fields vs improved superconductivity at low fields

G. Fuchs·S. -L. Drechsler·N. Kozlova·J. Freudenberger·M. Bartkowiak·J. Wosnitza·G. Behr·K. Nenkov·B. Buechner·L. Schultz

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Abstract

We report resistivity and upper critical field B_c2(T) data for As deficient LaO_(0.9)F_(0.1)FeAs_(1-delta) in a wide temperature and high field range up to 60 T. These disordered samples exhibit a slightly enhanced superconducting transition at T_c = 29 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. This flattening is interpreted as Pauli limiting behaviour (PLB) with B_(c2)(0) approx 63 T. We compare our results with B_(c2)(T)-data reported in the literature for clean and disordered samples. Whereas clean samples show no PLB for fields below 60 to 70 T, the hitherto unexplained flattening of B_(c2)(T) for applied fields H || ab observed for several disordered closely related systems is interpreted also as a manifestation of PLB. Consequences of our results are discussed in terms of disorder effects within the frame of conventional and unconventional superconductivity.

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G. Fuchs, S. -L. Drechsler, N. Kozlova, J. Freudenberger, M. Bartkowiak, J. Wosnitza, G. Behr, K. Nenkov, B. Buechner, L. Schultz. 2009-05-29. Upper critical field measurements up to 60 T in arsenic-deficient LaO_(0.9)F_(0.1)FeAs_(1-delta): Pauli limiting behaviour at high fields vs improved superconductivity at low fields. https://doi.org/10.1007/s10909-009-0145-z

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