Elucidation of the electronic state and the mechanism of the undoped superconductivity in the genuine T'-type cuprates

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H02915
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Tohoku University
• Principal Investigator: KOIKE Yoji 東北大学, 工学研究科, 名誉教授 (70134038)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 高温超伝導 / 銅酸化物 / ノンドープ超伝導

Outline of Final Research Achievements

We have succeeded in synthesizing electron-doped and hole-doped polycystalline samples of T'-La1.8Eu0.2CuO4-yFy and T'-La1.8-xEu0.2SrxCuO4. The carrier-doping dependence of Tc has been clarified. From NMR and muon spin relaxation measurements, it has been concluded that the superconductivity has d-wave symmetry due to the spin fluctuations. The origin of superconducting carriers may be due to the collapse of the so-called charge-transfer gap, but this has not yet been settled. Moreover, various measurements have been carried out for single crystals of electron-doped T'-Pr1.3-xLa0.7CexCuO4. It has been found that antiferromagnetic fluctuations are large in these crystals and it has also been concluded that the superconductivity has d-wave symmetry due to the spin fluctuations.

Free Research Field

低温電子物性

Academic Significance and Societal Importance of the Research Achievements

キャリアドーピングなしでも超伝導になる真性T’構造銅酸化物の真の物性相図を完成させた本研究は、「銅酸化物における高温超伝導はモット絶縁体へのキャリアドーピングによって発現する」という常識を打ち破り、超伝導機構の多様性を示したことは非常に大きな意義がある。
真性T’構造銅酸化物は、銅の周りの酸素が４配位であるという特徴を有しており、他の４配位銅酸化物の研究への波及効果が期待できる。