Critical Scaling of the Fluctuation Conductivity for ReFeAsO (Re=Nd,Pr) Superconductors

It is studied within the scaling analysis the fluctuation conductivity under the magnetic fields in ReFeAsO (Re=Nd, Pr) superconductors reported in literatures. A crossover is firstly observed in these iron-based superconductors from the Lowest Landau level (LLL) regime above the magnetic field H _LLL∼6–7 T to the critical fluctuation region at the low field. The static exponent ν of ReFeAsO superconductors is estimated to be 1.85±0.05, which is close to that of Bi₂Sr₂CaCu₂O₈, and the dynamic exponent z of ReFeAsO superconductors deviates from the theoretical prediction but is similar to that extracted from the resistivity experiment using the crossing-point technique.