UTe₂, an unconventional superconductor, exhibits a reentrant superconducting state at magnetic fields between 40 and 70 Tesla—but only when the field is perfectly aligned and temperatures hover near absolute zero.
The Discovery
Researchers at the Institute of Science and Technology Austria (ISTA), led by assistant professor Kimberly Modic and PhD student Valeska Zambra, have identified the mechanism behind this mysterious high-field state in uranium ditelluride (UTe₂).
The team found a region of large transverse magnetic susceptibility in UTe₂, which likely acts as the 'glue' for electron pairing, explaining the reentrant superconductivity.
This provides direct evidence that magnetic fluctuations underpin the high-field superconducting state—even though UTe₂ is not magnetic in its normal state.
The Challenge
Studying UTe₂ required measuring transverse magnetic susceptibility under extreme conditions:
- Pulsed magnetic fields up to 60 Tesla
- Temperatures near absolute zero
- Samples smaller than a grain of sand (about the thickness of a human hair) to ensure defect-free measurements
The Breakthrough Method
The ISTA team developed a novel approach:
The technique involves placing a microscopic sample on a cantilever and shaking it in a pulsed magnetic field, allowing detection of magnetic fluctuations that were previously impossible to measure.
This measurement technique is now being adopted by other high-field laboratories worldwide.
Publication Details
The research was published in Nature Communications (DOI: 10.1038/s41467-026-71899-7).