Identifying the magnetic fingerprint of superconductivity

Using powerful pulsed magnetic fields, Los Alamos researchers and their collaborators have unlocked new understanding of how electronic structure and magnetism influence superconducting behavior. In three different studies, the researchers demonstrated the use of extreme magnetic fields as a tool that exposes the intertwined nature of unconventional superconductivity, magnetism and novel quantum states.

Read the papers:
Nature Physics: Observation of the Yamaji effect in a cuprate superconductor  
Science: High-field superconducting halo in UTe₂ 
Proceedings of the National Academy of Sciences: High-magnetic-field phases in U₁₋ₓThₓTe

Why this matters: Understanding the mechanisms at work in superconductivity could guide the search for materials that conduct electricity with zero resistance at ever-higher magnetic fields and temperatures. Such materials could have applications in future energy and quantum technologies.

What they did: Across the three studies, the researchers

• Used strong magnetic fields — up to about 75 tesla — to study how electrons behave in superconductors.
• Rotated the magnetic field’s direction while measuring changes in electrical resistance to reveal the material’s underlying electronic structure.
• Probed three related systems: the high-temperature cuprate superconductor HgBa2CuO4+ð, the uranium-based heavy-fermion superconductor UTe2 and a thorium-doped version of UTe2, U1-xThxTe2.

What they learned:

• In Nature Physics, the researchers discovered subtle ripples — known as the Yamaji effect — in the high-temperature cuprate superconductor, experimentally confirming the presence of “Fermi-surface pockets.” This observation of how electrons arrange themselves just before superconductivity sets in refines the understanding of what triggers the phenomenon in these materials.
• In Science, the team discovered a rare, high-field “halo” phase of superconductivity wrapping around UTe2’s magnetic axis. The results show that strong magnetic fields can enhance superconductivity — rather than destroy it — challenging conventional theory and pointing toward exotic new forms of the phenomenon.
• In PNAS, the researchers showed that small substitutions of thorium in UTe2 disrupts or erases some of the compound’s unusual superconducting phases. This work reveals the complex elements driving the phenomenon and offers a path for potentially tuning superconductivity through chemical composition.

Funding: These works were partially performed at the National High Magnetic Field Laboratory Pulsed Field Facility, which is funded by the National Science Foundation and the state of Florida and U.S. Department of Energy. The Los Alamos portions of these works were supported by Los Alamos' Laboratory Directed Research and Development program and/or a “Science of 100T” grant from DOE’s Basic Energy Sciences program.

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