Neutron scattering study on magnetic fluctuations in spin-triplet superconductor Sr2RuO4

• Project/Area Number: 17K14349
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: 一般財団法人総合科学研究機構(総合科学研究センター(総合科学研究室)及び中性子科学センター(研究開発
• Principal Investigator: Iida Kazuki 一般財団法人総合科学研究機構(総合科学研究センター(総合科学研究室)及び中性子科学センター(研究開発, 中性子科学センター, 研究員 (00721987)
• Project Period (FY): 2017-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2017: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
• Keywords: 非従来型超伝導 / 中性子非弾性散乱 / スピン三重項超伝導 / 磁気揺らぎ / 物性実験

Outline of Final Research Achievements

Sr2RuO4 is the strong candidate for a chiral p-wave superconducting material, and thus is extensively investigated so far. However, the nature of its superconductivity, especially the superconducting order parameter is still a matter of intense debate. To answer the remaining issue on Sr2RuO4, we investigated by means of inelastic neutron scattering spectroscopy. We have succeeded in observing the band-dependent magnetic fluctuations and the spin gap at the incommensurate magnetic fluctuations. Furthermore, we investigated in detail the L dependence of the low energy incommensurate magnetic fluctuations, which reveal that the superconducting gap has a horizontal line node. These results can give the strong constraint to determine the superconducting order parameter in Sr2RuO4 leading to fully understand the nature of its superconductivity.

Academic Significance and Societal Importance of the Research Achievements

本研究では、非弾性中性子散乱の手法よってSr2RuO4の超伝導ギャップ関数が水平ラインノードを持つことを解明した。この結果はSr2RuO4の超伝導関数の対称性が、従来報告されていたchiral p波の超伝導ではなくspin singletである事を強く示唆している。Sr2RuO4はトポロジカル超伝導体の候補物質として提案されているが、本研究の結果はその提案の再考を促すものであり、それ故に有意義であると考えられる。一方で、spin tripletの起源となりうる強磁性揺らぎも観測されており、Sr2RuO4に関して今後のさらなる研究を促す効果も期待できる。

Research Products

• [Journal Article] Quantum magnetisms in uniform triangular lattices Li2AMo3O8 (A=In, Sc) (2019)
  • Author(s): Iida Kazuki、Yoshida Hiroyuki、Okabe Hirotaka、Katayama Naoyuki、Ishii Yuto、Koda Akihiro、Inamura Yasuhiro、Murai Naoki、Ishikado Motoyuki、Kadono Ryosuke、Kajimoto Ryoichi
  • Journal Title: Scientific Reports Volume: 9 Issue: 1 Pages: 1826-1826
  • DOI: 10.1038/s41598-018-36123-7
  • Peer Reviewed / Open Access
• [Journal Article] Time-of-flight elastic and inelastic neutron scattering studies on localized 4d electron layered perovskite compound La5Mo4O16 (2017)
  • Author(s): K. Iida, R. Kajimoto, Y. Mizuno, K. Kamazawa, Y. Inamura, A. Hoshikawa, Y. Yoshida, T. Matsukawa, T. Ishigaki, Y. Kawamura, S. Ibuka, T. Yokoo, S. Itoh, and T. Katsufuji
  • Journal Title: Journal of the Physical Society of Japan Volume: 86 Issue: 6 Pages: 064803-064803
  • DOI: 10.7566/jpsj.86.064803
  • Peer Reviewed
• [Journal Article] Spin resonance in the new-structure-type iron-based superconductor CaKFe4As4 (2017)
  • Author(s): K. Iida, M. Ishikado, Y. Nagai, H. Yoshida, A. D. Christianson, N. Murai, K. Kawashima, Y. Yoshida, H. Eisaki, and A. Iyo
  • Journal Title: Journal of the Physical Society of Japan Volume: 86 Issue: 9 Pages: 093703-093703
  • DOI: 10.7566/jpsj.86.093703
  • NAID: 210000134492
  • Peer Reviewed / Int'l Joint Research
• [Presentation] 中性子非弾性散乱によるSr2RuO4の磁気揺らぎ (2017)
  • Author(s): 飯田一樹
  • Organizer: 京都大学基礎物理学研究所研究会