Superconducting fluctuation probed by c-axis conductivity in YBa 2Cu 3O 7−δ single crystal

Abstract

Superconducting fluctuation of an untwinned YBCO single crystal is studied from measuring the c-axis electrical conductivity in magnetic fields up to 100 kOe parallel to the c-axis. The fluctuation conductivity curves above 10 kOe are not described by the three dimensional(3D) XY theory, but are well scaled on the universal curve based on the lowest Landau level(LLL) theory above H ≥ 20 kOe. These results indicate that the critical behavior of the untwinned YBCO is described by the LLL theory. We also point out the possibility that the crossover of the critical behavior from the LLL region to the 3D XY one occurs below 20 kOe.