The critical current density of iron-based superconductors under magnetic field

The time-dependent Ginzburg-Landau Lawrence-Doniach model with thermal fluctuations is used to investigate the critical current density. We calculate the critical current as a function of magnetic field and temperature in the homogeneous phase. The theoretical result based on the self-consistent Gaussian approximation is used to fit the measurement data of iron-based superconductors FeSe0.5Te0.5. Our results show good agreement with experimental data for temperatures at 4.2 and 12 K. We also plot several theoretical curves about the critical current density for temperatures below and above T-c. It shows that the critical current density is still non-zero and considerably large for temperature above T-c, indicating the residual superconductivity above T-c due to strong thermal fluctuations.