Upper critical field, penetration depth, and depinning frequency of the high-temperature superconductor LaFeAsO_(0.9)F_(0.1) studied by microwave surface impedance

摘要

Temperature-dependent and magnetic-field-dependent measurements of the microwave surface impedance of superconducting LaFeAsO_(0.9)F_(0.1) (T_c≈26 K) reveal a very large upper critical field (B_(c2) ≈ 56 T) and a large value of the depinning frequency (f_0≈6 GHz); together with an upper limit for the effective London penetration depth, λ_(eff) ≤ 200 nm, our results indicate a strong similarity between this system and the high-T_c superconducting cuprates.