High-temperature superconductors: Vortex-glass transition unveiled

The motion of vortices in high-T_c superconductors is a crucial property in the selection of materials suitable for technological applications. At the same time, studies in this field also lead to fascinating insights about the fundamental physics of an ensemble of flux lines, both in mutual interaction among themselves and influenced by the physical parameters of the host material (dimensionality, superconducting anisotropy, but also impurities and defects or, more generally, quenched disorder), as well as by external parameters. This branch of research has been driven by the discovery of iron-based pnictide superconductors, whose peculiar properties (low superconducting anisotropies, high values of both high-T_c and high-H_c2) attract a huge amount of interest both in view of its potential applications and for basic research. In J. Phys.: Condens. Matter 25 505701, we discuss our recent investigation of optimally-doped single crystals of Ba(Fe_1-xCo_x)₂As2 by means of magneto-resistivity and magnetic ac susceptibility measurements.