Strange Form of Superconductivity “Stuns” Scientists

A newly mapped form of superconductivity in uranium ditelluride emerges only under extremely strong magnetic fields, defying long-held expectations about how superconductors behave.

A puzzling form of superconductivity that arises only under strong magnetic fields has been mapped and explained by a research team that includes Andriy Nevidomskyy, professor of physics and astronomy at Rice University. Their findings, published in Science, describe how uranium ditelluride (UTe₂) develops a superconducting halo when exposed to intense magnetic fields.

Traditionally, scientists have viewed magnetic fields as harmful to superconductors. Even moderate magnetic fields typically weaken superconductivity, while stronger ones can destroy it once a known critical threshold is exceeded.

However, UTe₂ challenged these expectations. In 2019, researchers discovered that the material could maintain superconductivity in magnetic fields hundreds of times stronger than those tolerated by conventional superconductors.

“When I first saw the experimental data, I was stunned,” said Nevidomskyy, a member of the Rice Advanced Materials Institute and the Rice Center for Quantum Materials. “The superconductivity was first suppressed by the magnetic field as expected but then reemerged in higher fields and only for what appeared to be a narrow field direction. There was no immediate explanation for this puzzling behavior.”

Superconducting resurrection in high fields

The phenomenon was first identified by researchers at the University of Maryland (UMD) and the National Institute of Standards and Technology (NIST) and quickly drew global attention from physicists. In UTe₂, superconductivity disappears below 10 tesla—a magnetic field already considered extremely strong by conventional standards.

Unexpectedly, superconductivity reappears once the field strength exceeds about 40 tesla.

This surprising revival has been dubbed the Lazarus phase. Researchers determined that the phase depends critically on the angle of the magnetic field relative to the crystal’s structure.

Working with experimental collaborators at UMD and NIST, Nevidomskyy helped map the angular dependence of this high-field superconducting state. Their measurements revealed that the superconducting phase forms a toroidal, or doughnut-shaped, halo surrounding a specific crystalline axis.

“Our measurements revealed a three-dimensional superconducting halo that wraps around the hard b-axis of the crystal,” said Sylvia Lewin of NIST, a co-lead author on the study. “This was a surprising and beautiful result.”

Building theory to fit halo

To explain the observations, Nevidomskyy developed a theoretical model capable of reproducing the experimental results without relying heavily on debated microscopic mechanisms.

Instead, the approach used an effective phenomenological framework that required only a minimal set of assumptions about the pairing forces that bind electrons into Cooper pairs.

The model successfully reproduced the unusual angular dependence observed in experiments, helping clarify how the orientation of a magnetic field influences superconductivity in UTe₂.

Deeper understanding of interplay

The research team found that the theory, fitted with a few key parameters, aligned remarkably well with the experimental features, particularly the halo’s angular profile. A key insight from the model is that Cooper pairs carry intrinsic angular momentum like a spinning top does in classical physics. The magnetic field interacts with this momentum, creating a directional dependence that matches the observed halo pattern.

This work lays the foundation for a deeper understanding of the interplay between magnetism and superconductivity in materials with strong crystal anisotropy like UTe2.

“One of the experimental observations is the sudden increase in the sample magnetization, what we call a metamagnetic transition,” said NIST’s Peter Czajka, co-lead author on the study. “The high-field superconductivity only appears once the field magnitude has reached this value, itself highly angle-dependent.”

The exact origin of this metamagnetic transition and its effect on superconductivity is hotly debated by scientists, and Nevidomskyy said he hopes this theory would help elucidate it.

“While the nature of the pairing glue in this material remains to be understood, knowing that the Cooper pairs carry a magnetic moment is a key outcome of this study and should help guide future investigations,” he said.

Reference: “High-field superconducting halo in UTe2” by Sylvia K. Lewin, Peter Czajka, Corey E. Frank, Gicela Saucedo Salas, G. Timothy Noe II, Hyeok Yoon, Yun Suk Eo, Johnpierre Paglione, Andriy H. Nevidomskyy, John Singleton and Nicholas P. Butch, 31 July 2025, Science.
DOI: 10.1126/science.adn7673

Co-authors of this study include Corey Frank and Nicholas Butch from NIST; Hyeok Yoon, Yun Suk Eo, Johnpierre Paglione and Gicela Saucedo Salas from UMD; and G. Timothy Noe and John Singleton from the Los Alamos National Laboratory. This research was supported by the U.S. Department of Energy and the National Science Foundation.

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