磁場を味方にするウラン超伝導の機構を解明～自らを柔軟に変化させ、耐えられる磁場の限界を2倍に～

2025-09-25 日本原子力研究開発機構,東北大学,京都大学

スピン三重項超伝導の概念図。中央の矢印は磁場の方向と強さを表す。磁場中で超伝導はその状態を柔軟に変え、より強い磁場に適応した新しい状態へ自ら移行する

＜関連情報＞

• https://www.jaea.go.jp/02/press2025/p25092501/
• https://journals.aps.org/prl/abstract/10.1103/z8yx-yzdh

スピン三重項超伝導体UTe2の秩序パラメータの自己再構築 Self-Reconstruction of Order Parameter in Spin-Triplet Superconductor UTe2

Y. Tokiwa, P. Opletal, H. Sakai, K. Kubo, S. Kambe, E. Yamamoto, M. Kimata, S. Awaji, T. Sasaki et al.
Physical Review Letters  Published: 24 September, 2025
DOI: https://doi.org/10.1103/z8yx-yzdh

Abstract

We investigate the effect of easy-axis metamagnetic crossover on superconductivity in UTe₂ along the axis through measurements of ac susceptibility, magnetization, and the magnetocaloric effect. In ultraclean single crystals, we identify a field-induced phase transition within the superconducting state at 5.6 T, driven by metamagnetism. This transition leads to a high-field superconducting state, significantly increasing the upper critical field to 12 T. A sudden increase in entropy at the transition suggests a self-reconstruction of the order parameter, enabling multicomponent superconducting states to adapt to external perturbations.