Thermally activated flux flow and fluctuation conductivity in LiFeAs single crystal

¹ Department of Physics, Sungkyunkwan University - Suwon 440-746, Republic of Korea
² Department of Physics, Chungbuk University - Cheongju 361-763, Republic of Korea
³ Department of Applied Physics, Kyung Hee University - Yongin 446-701, Republic of Korea

^a yskwon@skku.ac.kr

Received: 12 October 2011
Accepted: 19 January 2012

Abstract

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.