For forty years, researchers of high-temperature superconductors based on copper believed that their crystals were uniform throughout. A new study by scientists from the University of Warwick and the European Synchrotron Radiation Facility (ESRF) has shown the opposite: the material is a mosaic of different structures.
The discovery of 1986 — cuprates — promised a revolution in lossless energy transmission. All theories and calculations were built on the idea of a single crystal lattice. Now that idea has been refuted.
Using three-dimensional X-ray diffraction (3DXRD), the team peered deep inside a sample of LESCO — a lanthanum-europium-strontium cuprate — for the first time. Scanning from room temperature down to 100 kelvins revealed two different atomic packings separated by unusually wide boundaries — about 150 nanometers.
According to chemist Mark Senn, these boundaries do not merely separate regions but actively hinder superconductivity. Electrons that should form pairs and move without resistance encounter obstacles in these zones.
The result explains why some samples perform better than others and calls for a revision of many previous measurements. Future models must take this internal inhomogeneity into account.
The 3DXRD method, made possible by the ESRF upgrade, will reveal similar "hidden" structures in other materials as well. The question now is whether to consider the cuprate a single substance or a collection of several materials within one crystal.
Understanding the real structure brings the practical application of superconductors at higher temperatures closer.
