Thermally activated flux flow and fluctuation conductivity in LiFeAs single crystal

The thermally activated flux flow (TAFF) of a LiFeAs single crystal was studied in magnetic fields up to 9 T. The thermally activated energy (TAE) was analyzed using a conventional Arrhenius relation and a modified TAFF theory. The modified TAFF method results are in better agreement with experimental data than the Arrhenius ones. Through the analysis of the modified TAFF method, we found that the LiFeAs superconductor is regarded as a three-dimensional (3D) system in the TAFF region. In addition, we obtained the vortex-glass temperature T _g from the linear region of the (dln ρ/dT) ^{- 1}. And the fluctuation conductivity was analyzed for the LiFeAs superconductor using Aslamazov-Larkin (AL) theory and the lowest Landau level (LLL) scaling, in zero and nonzero magnetic fields. With the determined values of T _c(H), the fluctuation conductivity was scaled within a 3D-LLL approach. Compared with the NMR result of the 2D antiferromagnetic spin fluctuation, these results imply that LiFeAs exhibited a 2D-3D crossover of the fluctuation conductivity (FC) with decreasing temperature.