Nuclear Magnetic Resonance study of the charge density wave order in the Cu oxide superconductor

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03747
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Okayama University
• Principal Investigator: Kawasaki Shinji 岡山大学, 自然科学学域, 准教授 (80397645)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 銅酸化物高温超伝導 / 核磁気共鳴 / 電荷密度波

Outline of Final Research Achievements

We have conducted nuclear magnetic resonance (NMR) experiments to elucidate the origin of the novel charge density wave order in Cu-oxide (cuprate) superconductor, which is the most promising candidate for room-temperature superconductivity among known superconductors. From systematic measurements, we have obtained new findings that indicate the importance of "charge fluctuation" in addition to spin fluctuation, which has been believed to be the origin of high-temperature superconductivity. Based on our results, further developments of physics of the cuprate superconductivity in theoretical and experimental studies focusing on charge fluctuations are expected. Another purpose of the study was to introduce uniaxial strain, a new external parameter that has recently been the focus of much attention in condensed matter physics, into NMR experiments, and we succeeded in developing an laboratory-made piezoelectric uniaxial strain cell during the research period.

Free Research Field

強相関電子系

Academic Significance and Societal Importance of the Research Achievements

「超伝導」は将来の脱炭素社会実現に向け有効な省エネ技術の一つであるが、室温超伝導物質がなく、超伝導利用には低温寒剤など超伝導維持コストが普及を妨げている。銅酸化物高温超伝導体は室温超伝導最有力候補物質であるが、超伝導発現機構は不明で室温超伝導開発指針もない。本研究は、銅酸化物の未解明電子状態「擬ギャップ」の起源解明の鍵とされる電荷密度波秩序の研究を実施した。結果、銅酸化物の物理において重要と信じられてきた磁気揺らぎに加え「電荷」揺らぎが重要である証拠を得た。今後高温超伝導発現機構を考える上で電荷に着目した理論や実験研究の発展が期待出来る。さらには将来の脱炭素社会実現に寄与できる。