Observation of anisotropic diamagnetism above the superconducting transition in iron-pnictide Ba_(1-x)K_xFe2As2 single crystals due to thermodynamic fluctuations

TL;DR

This study reveals anisotropic diamagnetism above the superconducting transition in Ba_(1-x)K_xFe2As2 crystals, attributed to thermodynamic fluctuations, and supports a 3D anisotropic Ginzburg-Landau model for iron pnictides.

Contribution

First experimental evidence of anisotropic diamagnetism above Tc in iron-pnictide superconductors explained by Gaussian Ginzburg-Landau theory.

Findings

Diamagnetism observed above Tc due to thermally activated Cooper pairs

Anisotropic diamagnetism depends on magnetic field orientation

Supports 3D anisotropic Ginzburg-Landau description

Abstract

High resolution magnetization measurements performed in a high quality Ba_(1-x)K_xFe2As2 single crystal allowed to determine the diamagnetism induced above the superconducting transition by thermally activated Cooper pairs. These data, obtained with magnetic fields applied along and transverse to the crystal ab layers, demonstrate experimentally that the superconducting transition of iron pnictides may be explained at a phenomenological level in terms of the Gaussian Ginzburg-Landau approach for three-dimensional anisotropic superconductors.