The Big Surprise: High-Temperature Superconductivity
The discovery of high-temperature superconductors in 1986 started worldwide tremendous research activities which quickly resulted in the preparation of superconductors with a critical temperature above 130 K. These cuprate superconductors are highly anisotropic, with superconductivity residing in the copper-oxide planes. Initially, the granular structure of the ceramic materials needed to be optimized. Much progress was achieved by fabricating epitaxial films. The symmetry of the wave function of the Cooper-pair condensate represents an important issue. Today, the Josephson effect of a single grain boundary is used in SQUIDs. The intrinsic Josephson effect in small multi-layer crystals is explored as a source of terahertz radiation. Major events were the discovery of superconductivity in MgB2 in 2001 and in iron-pnictides in 2008.