High-field Pauli-limiting Behavior And Strongly Enhanced Upper Critical Magnetic Fields Near The Transition Temperature Of An Arsenic-deficient Lao_(0.9)f_(0.1)feas_(1-δ) Superconductor

摘要

We report upper critical field B_(c2)(T) data for disordered (arsenic-deficient) LaO_(0.9)F_(0.1)FeAs_(1-δ) in a wide temperature and magnetic field range up to 47 T. Because of the large linear slope of B_(c2) ≈ -5.4 to -6.6 T/K near T_c ≈ 28.5 K, the T dependence of the in-plane B_(c2)(T) shows a flattening near 23 K above 30 T which points to Pauli-limited behavior with B_(c2)(0) ≈ 63-68 T. Our results are discussed in terms of disorder effects within conventional and unconventional superconducting pairings.