Scientists at the SLAC National Accelerator Laboratory in California have discovered a surprising 3D arrangement of electrons in a high-temperature superconductor. Superconductors are materials that, at certain temperatures (usually close to absolute zero), transmit electricity without resistance.

This research could help us better understand how superconductors work, and perhaps eventually lead to superconductors that operate near room temperature, as all superconductors (even high-temperature ones) operate far below the freezing point of water.

The researchers used a type of cuprate (specifically yttrium barium copper oxide, YBa₂Cu₃O_6.67) and exposed it to an X-ray free-electron laser combined with a pulse magnet, a million times stronger than Earth’s magnetic field. The intense magnetic pulses managed to suppress the superconductive properties of the material, which made it possible for the group to use the laser to observe how the electrons were arranged.

Near absolute zero, the electrons in certain materials tend to organize themselves into a charge density wave (CDW): This wave is not like a wave in a pond, it is a static distribution of electrons. So far, these CDWs were only observed in 2D, but the SLAC team – using SLAC’s Linac Coherent Light Source (LCLS) X-ray laser – observed a 3D distribution of electrons. 

“This was totally unexpected, and also very exciting,” said Jun-Sik Lee, a SLAC staff scientist and one of the leaders of the experiment, in a statement. “This experiment has identified a new ingredient to consider in this field of study. Nobody had seen this 3-D picture before. This is an important step in understanding the physics of high-temperature superconductors.”

CDWs were theoretically predicted in the 1930s, but the first one was only observed in 2012. Since their discovery, scientists have been unearthing more and more evidence linking CDWs and superconductors. 

The latest finding highlights the highly complex nature of cuprates, and the many properties that need to be taken into account when characterizing superconductors. The team wants to perform follow-up experiments to provide a detailed description of the effect and to find out if it is present in other types of high-temperature superconductors.

The paper is published in the journal Science.