Disorder Effects on μSR Measurements of the Magnetic Penetration Depth of Iron-arsenic Superconductors

We use a molecular dynamics method to generate a high degree of random frozen disorder of a vortex lattice in a type-II superconductor. By calculating the magnetic field distribution, we show that such strong deviation from a perfect vortex lattice has a profound influence on the measured transverse-field (TF) μSR line shape of a real superconductor. The results have implications for measurements of the magnetic penetration depth λ in the bulk of high-temperature iron-arsenic superconductors.