Elucidation of the mechanism of the new superconductivity without doping in T'-type cuprates

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05458
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Sophia University
• Principal Investigator: Adachi Tadashi 上智大学, 理工学部, 教授 (40333843)
• Research Collaborator: SUMURA takuya ; KAWABATA koki ; PARK sangeun ; BAQIYA malik anjelh ; KURASHIMA koshi ; ONISHI shusei
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 高温超伝導体 / 電子ドープ型銅酸化物 / 母物質ノンドープ超伝導 / 還元処理 / ミュオンスピン緩和 / Ｘ線吸収分光

Outline of Final Research Achievements

In order to elucidate the mechanism of superconductivity in the parent compounds of the electron-doped high-Tc cuprate superconductors with the T'-structure, we have investigated detailed changes of the electronic states through the reduction annealing from the electrical resistivity, muon spin relaxation etc. using single crystals of the T'-cuprates.
By improving the reduction annealing, we have succeeded in removing effectively the excess oxygen from the single crystals of the T'-cuprates. It has been clarified that not only electrons but also holes are generated through the reduction annealing in the T'-cuprates, suggesting that holes are related to the appearance of superconductivity. Moreover, it has been clarified that the Cu-spin correlation and superconductivity are in intimate relation with each other in the T'-cuprates.

Free Research Field

超伝導物性学

Academic Significance and Societal Importance of the Research Achievements

本研究の結果、電子ドープ型T'銅酸化物から過剰な酸素を効果的に取り除く方法を確立した。これは、他の遷移金属酸化物に対しても利用できる技術なので、様々な機能性酸化物の開発に貢献するだろう。
本研究から、T'銅酸化物において還元とともに電子状態がどのように変化するのかが明らかになった。特に、超伝導が発現する試料におけるホールキャリアの存在とCuスピン相関の発達を結論できたことは特筆に値する。今後は、元素置換によらない新たなキャリアドープ法による新規高温超伝導体の創製が発展するだろう。