A material that carries electricity without resistance may be held back by its own structure, challenging 40 years of assumptions about copper-based superconductors.

A crystal that scientists thought had the same structure throughout is actually a patchwork of two subtly different arrangements of atoms. The boundaries between those regions are hundreds of times wider than expected, so broad that they behave almost like a structure in their own right rather than a simple dividing line.

The material belongs to a family called cuprates, copper-based superconductors that can carry electricity without resistance at unusually high temperatures for superconductivity, although those temperatures are still very cold. High-temperature superconductivity underpins research into future power grids, medical scanners, and quantum computers. Its promise also includes magnets far more powerful than those possible today.