A new quantum mystery emerges with the strange superconductor UTe2, which exhibits “reentry superconductivity”—losing its superconducting state as a magnetic field strengthens, only to regain it at even higher field intensities.
Superconductors are materials that allow electricity to flow without resistance, though typically only at extremely low temperatures, and their research may be the key to producing the next generation of quantum technologies.
This bizarre new quirk of superconductivity, discovered by scientists at the Institute of Science and Technology Austria (ISTA), was reportedly uncovered during the development of a new high-field measurement technique, as revealed in a recent paper in Nature Communications.
Quantum Superconductor Research
Some areas of quantum research are so far ahead of practical application that their benefits may not be realized for years or even decades. Still, the pursuit of these mysteries continues to drive scientific discovery. One such case is the unusual quantum material that captured the attention of ISTA researchers: the superconductor uranium ditelluride, UTe₂.
“It seems like each measurement on UTe2 uncovers yet another mystery. Our work now presents evidence for the mechanism behind some of these mysteries,” said co-author Kimberly Modic, assistant professor at ISTA.
Magnetic field strength is measured in units called Tesla, with one Tesla roughly equivalent to the force needed to lift a small automobile. Most superconductors lose their properties under strong magnetic fields—as UTe₂ does at around 10 Tesla. However, between 40 and 70 Tesla, superconductivity reappears, a phenomenon known as reentrant superconductivity.
Reentry Superconductivity
At very low temperatures, conventional superconductors allow electrons to pair up and move without resistance. However, this standard explanation does not fully account for the behavior observed in UTe₂.
“So far, researchers have assumed that something magnetic must be behind superconductivity in unconventional superconductors,” Modic explained.
Other uranium-based superconductors that exhibit reentrant superconductivity, such as UCoGe and URhGe, are magnetic, lending support to this idea. However, UTe₂ itself is not magnetic, leaving open the question of how it achieves its unusual superconducting state. Notably, UTe₂ exhibits reentrant superconductivity at temperatures even colder than the vacuum of space, and only when the magnetic field is aligned in a specific direction.
“Although other unconventional superconductors exist, UTe2 makes the word ‘unconventional’ almost sound like an understatement,” Modic commented.
Examine Reentry Superconductivity
To better understand how this phenomenon emerges, researchers focused on the conditions that precede the reappearance of superconductivity. Using pulsed magnetic field facilities, they rapidly increased the field strength from 0 to 60 Tesla in just a tenth of a second. This allowed them to investigate whether magnetic fluctuations within the material could explain the behavior.
To capture these rapid, small-scale changes, the ISTA team developed a new high-field measurement technique.
“We devised a method that allows us to interrogate the sample under extreme magnetic fields by giving it a controlled wiggle,” explained lead author Valeska Zambra, a PhD student.
“We place the sample on a cantilever—a sort of stick—to manipulate and shake it in the magnetic field,” Zambra said. “From the crystal’s point of view, the shaking makes it look like the direction of the magnetic field oscillates in time, allowing for a fast check of the magnetization under that changing field. This allows us to measure an important property called ‘transverse magnetic susceptibility’ that no one has accessed under these conditions.”
From their investigations, the team identified a large transverse magnetic susceptibility region in UTe2, enabling electrons to bind under such strong magnetic fields.
Working in Tiny Scales
The researchers specialize in working with extremely small samples—some smaller than a grain of sand—made possible by their new technique, which is now being adopted by other teams.
“Measuring small samples roughly as large as the thickness of a human hair is especially challenging, but this is precisely what our group specializes in,” Modic explained. “While many techniques can only be applied to larger crystals, Valeska’s method, developed in our group at ISTA, comes with the added advantage that it also works in high magnetic fields where the toolbox of available techniques is already very limited.”
“Often, scientists realize the usefulness of a new finding years or decades later,” Zambra said. “The accidental discovery of superconductivity over a century ago eventually led to the development of the medical imaging technique MRI.”
“We might be looking at a completely new type of superconductivity for which we have not yet imagined applications,” Modic says. “Will it be useful for something down the road? I don’t know.”
“It’s a mystery,” Modic concluded, “and mysteries are worth going after.”
The paper, “Giant Transverse Magnetic Fluctuations at the Edge of Re-Entrant Superconductivity in UTe2,” appeared in Nature Astronomy on April 29, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.