New Form of Superconductor Behavior Discovered That We've Never Seen BeforeNEWS | 19 October 2026Materials in a superconducting state are of huge interest to scientists.
That's because of rare properties – primarily the ability to conduct electricity with zero resistance, with nothing lost to heat – that promise to transform computing, energy grids, and transport.
This phenomenon happens when free electrons condense into a low-energy quantum state at very cold temperatures, pairing up into what are called Cooper pairs so they can zip through materials without interference.
Back in 2007, scientists predicted the existence of a more exotic type of electron movement, called a pair density wave (PDW), where the Cooper pairs form specific patterns while moving, like ripples on sand.
Now a team led by researchers from the University of Illinois at Urbana-Champaign has found compelling evidence of PDWs on the surface of the metal uranium ditelluride, with their results published in PNAS.
What's more, the patterns were found to persist outside of the standard superconducting state, something that's never been seen before.
"Pair density waves are the Cheshire Cat's grin of superconductivity," says physicist Eduardo Fradkin from the University of Illinois at Urbana-Champaign.
"They are the vestige that remains once the phase itself has disappeared.
"In conventional superconductors, Cooper pairs form when the full phase transition occurs, but in this system, their observation in PDWs above the transition point shows that they are formed beforehand in a different state."
Rows of tellurium atoms, with the atomic arrangement bottom right and the top panel showing the repeating patterns – interpreted as evidence of PDWs. (Zhu et al., PNAS, 2026)
Uranium ditelluride becomes a superconductor below about 2.1 Kelvin (about -271 °C or -456 °F) and is of particular interest to researchers as it's thought to be a rare 'spin-triplet' superconductor, in which paired electrons also have a tiny magnetic orientation.
Signs of PDWs had previously been detected in the metal, and here the researchers took a closer look using a custom-made, high-quality form of uranium ditelluride.
The material was probed via a vector magnetic field scanning tunneling microscope (STM), which can measure magnetic responses in multiple, arbitrary directions.
"A key advantage of our experiment was the newly developed vector-magnet equipment, which provides an unusually large magnetic-field range along multiple directions," says physicist Zhen Zhu from the University of Illinois at Urbana-Champaign.
"By systematically varying both the magnitude and direction of the field, together with temperature, we could track how these modes evolved and build confidence that the behavior we observed was intrinsic."
The researchers added theoretical models to explain the charge patterns they were seeing below the critical temperature required for superconductivity, and at a point significantly above it, too.
"Thanks to new methods for growing higher-quality samples, we were able to observe spectral signatures that respond to temperature and magnetic fields exactly as pair density waves should," says physicist Vidya Madhavan from the University of Illinois at Urbana-Champaign.
"We even showed that the modes persist above the temperature at which superconductivity disappears, a tell-tale theoretical prediction that has not been convincingly observed before now."
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This doesn't mean bulk superconductivity is happening in uranium ditelluride at higher temperatures, but it does help physicists understand how Cooper pairs function and how they can exist outside of the conventional superconducting state.
It could also help researchers better understand the physics needed to develop superconductors at higher temperatures. Such advances could eventually make these materials more widely usable.
There's another electron ripple state called charge density waves (CDWs), where some electrons take on non-uniform patterns. Understanding how these waves are connected to PDWs will be crucial in interpreting experimental results in the future.
"PDWs are tricky to analyze in real materials, because they behave like conventional superconductors in some experiments, and like CDWs in [others]," says physicist Julian May-Mann from Stanford University.
"Confirming the existence of a PDW requires both high-quality experimental data as well as careful theoretical analysis."
The research has been published in PNAS.Author: David Nield. Source
