Publication Date： September 26, 2024
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Why are Uranium Superconductors Robust to Magnetic Fields?
－Elucidating a New Mechanism of Superconductivity－
Fig. 1 Mechanism underlying the realization of high upper critical fields in uranium superconductor UTe2
In spin-triplet superconductors, magnetic fluctuations within materials promote electron pair (Cooper pair) formation that leads to the generation of superconductivity. These magnetic fluctuations increase as the strength of the applied magnetic field increases, which in turn strengthens bonds between electron pairs. Therefore, superconductivity becomes more stable and is less likely to be destroyed even under strong magnetic fields.
Because superconductors are generally very sensitive to magnetic fields, developing superconductors that operate stably under strong magnetic fields is a crucial challenge for the advancement of superconducting wires and quantum devices. A new type of superconductivity called "spin triplet" has been discovered in the uranium-containing superconductor UTe2 (uranium-tellurium compound). In addition, a phenomenon—the strengthening of superconductivity under strong magnetic fields—that overturns conventional wisdom has been confirmed.
In this study, we used nuclear magnetic resonance (NMR) spectroscopy to investigate the mechanism of the enhancement of superconductivity under strong magnetic fields. Our experiment revealed that upon applying a strong magnetic field, magnetic fluctuations within materials increase, thereby strengthening bonding between electron pairs (Cooper pairs) responsible for superconductivity (Fig. 1). Thus, a superconducting state resilient to magnetic fields is realized.
This discovery indicates that in spin-triplet superconductors, magnetism and superconductivity are deeply interconnected. Furthermore, this result suggests that by applying this principle, superconductors with strong magnetic-field resistance can be developed using compounds that do not contain uranium. Such superconductors are extremely important for developing high-performance superconducting wires and quantum devices; therefore, they hold remarkable potential for expanding the applications of superconducting technology.
This work was supported by JSPS KAKENHI Grant Number JP20KK0061.
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