超伝導の波に隠された「もう一つの周期」を発見！ ―共鳴軟X線散乱が解き明かす未踏の電子秩序―

2026-09-08 東北大学

図1. La系銅酸化物における絡み合った電子秩序の模式図。冷却に伴いCDW・スピン密度波・PDW相関・三次元超伝導が異なる温度領域で発達する。PDW変調は、主要なCDWの約2倍の実空間周期（4aに対して8a）を取り得る。

＜関連情報＞

• https://www.tohoku.ac.jp/japanese/2026/09/press20260908-01-subharmonic.html
• https://journals.aps.org/prb/abstract/10.1103/djbs-mcz5

La系銅酸化物におけるサブハーモニック電荷密度波相関の観測 Observation of subharmonic charge-density-wave correlations in La-based cuprates

J.-S. Lee, S. A. Kivelson, H. Lee, T. Wang, Y. Ikeda, T. Taniguchi, C.-T. Kuo, M. Fujita, and C.-C. Kao
Physical Review B  Published :31 August, 2026
DOI: https://doi.org/10.1103/djbs-mcz5

Abstract

Pair-density-wave (PDW) correlations have been proposed as an important ingredient in the complex phase diagram of high-Tc cuprates, yet bulk-sensitive experimental signatures remain scarce. Here, we report resonant x-ray scattering measurements revealing a subharmonic charge-density-wave (CDW) scattering response in Sr-doped 1/8⁢−La_1.875⁢Ba_0.125⁢CuO₄ (LBCO). The subharmonic response appears at approximately half the primary CDW ordering wave vector and emerges within a physically relevant temperature regime associated with the development of in-plane superconducting correlations. Comparable subharmonic behavior is also observed in a chemically distinct La-based cuprate, La_1.87⁢Sr_0.13⁢Cu_0.99⁢Fe_0.01⁢O₄ (LSCO), within the same stripe-ordered, layer-decoupled regime. Together, these observations identify a bulk-sensitive scattering signature that is consistent with PDW correlations in La-based superconducting cuprates.