Researchers have discovered and described an unusual form of superconductivity that only appears under very strong magnetic fields. The study, led in part by Rice University physicist Andriy Nevidomsky, science We then explain how uranium ditelluride (UTe2) forms a unique superconducting halo when exposed to strong magnetic conditions.
Under normal circumstances, magnetic fields destroy superconductors. Even relatively mild magnetic fields tend to weaken superconductivity, but stronger fields usually cause superconductivity to disappear completely once a critical limit is reached. UTe2 breaks this rule. In 2019, scientists discovered that common materials can maintain a superconducting state hundreds of times stronger than the magnetic fields they can withstand.
“When I first saw the experimental data, I was stunned,” said Nevidomsky, a member of the Rice Institute for Advanced Materials and the Rice Center for Quantum Materials. “Superconductivity was initially suppressed by the magnetic field as expected, but then reappeared at higher fields and only in what appeared to be the narrow field direction. This puzzling behavior could not be immediately explained.”
Superconductivity “resurrection” in extreme fields
This strange behavior was first observed by a team from the University of Maryland (UMD) and the National Institute of Standards and Technology (NIST), and quickly caught the attention of the entire physics community. In UTe2, superconductivity disappears below 10 Tesla, an already very strong magnetic field, but unexpectedly returns at field strengths above 40 Tesla.
Scientists have named this resurrection the Lazarus stage. This phase was found to strongly depend on the angle between the magnetic field and the crystal structure of the material.
Nevidomskyy, working with collaborators at UMD and NIST, helped map how this high-field superconductivity varies with direction. Their measurements showed that the superconducting regions form a toroidal, or toroidal, shape that surrounds specific axes within the crystal.
“Our measurements reveal a three-dimensional superconducting halo that wraps around the crystal’s hard b-axis,” said NIST’s Sylvia Lewin, co-first author of the study. “This was an amazing and beautiful result.”
Building a model to explain halos
To understand what was going on, Nevidomsky created a theoretical model that could explain the observations without relying heavily on uncertain microscopic details. This model uses a phenomenological approach and focuses on the overall behavior rather than the exact underlying mechanisms that cause electrons to become Cooper pairs.
The results agreed well with experimental data, especially the unusual way that superconductivity varies depending on the direction of the magnetic field. This model shows how orientation plays an important role in whether superconductivity persists or is revived in UTe2.
How magnetism and superconductivity interact
The study also revealed that Cooper pairs in this material behave as if they carry angular momentum, similar to rotating objects. When a magnetic field is applied, it interacts with this motion, creating a directional effect that produces the observed halo pattern.
This insight helps explain how magnetism and superconductivity can coexist in materials with strong directional properties like UTe2.
“One of the experimental observations is a sudden increase in the magnetization of the sample, which we call a metamagnetic transition,” said Peter Czajka of NIST, co-lead author of the study. “High-field superconductivity appears only when the magnetic field magnitude reaches this value, which itself is highly angle-dependent.”
Scientists are still debating the cause of this metamagnetic transition and how it affects superconductivity. Nebidomsky said the new model could help clarify this open question.
“Although the nature of the binding adhesive in this material is not yet understood, finding that the Cooper pair has a magnetic moment is an important result of this study and should guide future research,” he said.
Research team and support
Corey Frank and Nicholas Butch of NIST participated in this research. UMD’s Hyeok Yoon, Yun Suk Eo, Johnpierre Paglione and Gicela Saucedo Salas; G. Timothy Noe and John Singleton of Los Alamos National Laboratory; Funding was provided by the U.S. Department of Energy and the National Science Foundation.
