The superconducting fluctuation optical conductivity of iron-based superconductors

We investigate the superconducting fluctuation optical conductivity using the time-dependent Ginzburg-Landau Lawrence-Doniach model with thermal noise describing strong thermal fluctuation in iron-based superconductors. The superconducting fluctuation optical conductivity as temperature in the homogeneous phase is calculated. The experimental data of iron-based superconductors FeSe0.5Te0.5 are fitted using the theoretical result based on the self-consistent Gaussian approximation. Our results show the real and imaginary part of the superconducting fluctuation optical conductivity in a wide region around T-c are well described by the theoretical formula. The superfluid density is also in good agreement with the experimental data in both the superconducting state below T-c and the normal state above T-c. It shows that the superfluid density and the imaginary portion of the optical conductivity are still non-zero and considerably large for temperature above T-c, indicating the residual superconductivity above T-c due to strong thermal fluctuations.