Study on the changeover of the gap-function symmetry in electron doped cuprate superconductor

• Project/Area Number: 17K14348
• 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: Ikeuchi Kazuhiko 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 (90435595)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2018: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000); Fiscal Year 2017: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
• Keywords: 高温超伝導 / 銅酸化物 / ギャップ対称性 / 非弾性散乱実験 / 電子添加型銅酸化物超伝導 / 磁気励起スペクトル / 試料育成 / 格子振動測定 / 磁気励起の測定 / 格子振動測定実験準備 / 試料育成環境整備 / 固体物理学

Outline of Final Research Achievements

We performed inelastic neutron scattering (INS) and inelastic x-ray scattering (IXS) experiments to investigate a possible changeover of the superconducting gap symmetry due to electron doping ratio into the 214 type cuprate system. Phonon branches exhibit characteristic softening at low energy region below a certain energy, thought to be the superconducting gap. The temperature dependence can be consistently understood with a d-wave gap formation, having amplitude at around q = (pi, 0) and nodes along (pi, pi) direction, on the Fermi surface of this system associating with the superconductivity. In addition, the INS with chopper spectrometer effectively showed that the magnetic excitation exhibits paramagnon behavior and no-change against temperature change around the superconducting transition temperature on its energy spectra. These results will lead to open the way for studying the gap symmetry owing to directly observing the quasi particle excitations.

Academic Significance and Societal Importance of the Research Achievements

銅酸化物系にみられる超伝導の特徴は、母相であるMott絶縁相に電子を注入しても正孔を注入しても、絶縁相近傍の金属領域において、高い転移温度を持って発現する点である。しかし、超伝導状態を含めた相図上の電子正孔対称性は、いまだ自明ではない。本研究結果は、準粒子励起の振る舞いを解明するものであり、電子濃度の変化に伴う超伝導状態の微視的共存・競合状態の理解に資する。さらには、種々エキゾチック超伝導の発現機構と密接に関連する、量子臨界点近傍における普遍的な振る舞いの解明につながるものと期待している。

Research Products

• [Journal Article] Al-impurity-induced magnetic excitations in heavily over-doped La1.7Sr0.3Cu0.95Al0.05O4 (2018)
  • Author(s): K. Ikeuchi, K. Nakajima, S. Ohira-Kawamura, R. Kajimoto, S. Wakimoto, K. Suzuki, and M. Fujita
  • Journal Title: AIP Advances Volume: 8 Issue: 10 Pages: 101318-101318
  • DOI: 10.1063/1.5043077
  • Peer Reviewed / Open Access
• [Journal Article] Fe-impurity-induced magnetic excitations in heavily over doped La1.7Sr0.3Cu0.95Fe0.05O4 (2018)
  • Author(s): K. Ikeuchi, T. Kikuchi, K. Nakajima, R. Kajimoto, S. Wakimoto, M. Fujita
  • Journal Title: J. Phys. Conf. Series Volume: 969 Pages: 012024-012028
  • DOI: 10.1088/1742-6596/969/1/012024
  • Peer Reviewed / Open Access
• [Journal Article] Detailed study of the structure of the low-energy magnetic excitations in overdoped La1.75Sr0.25CuO4 (2018)
  • Author(s): K. Ikeuchi, T. Kikuchi, K. Nakajima, R. Kajimoto, S. Wakimoto, M. Fujita
  • Journal Title: Physica B Volume: 536 Pages: 717-719
  • DOI: 10.1016/j.physb.2017.11.022
  • Peer Reviewed / Open Access
• [Presentation] Detailed study of temperature dependence of spin fluctuations in FeSe0.5Te0.5 (2019)
  • Author(s): K. Ikeuchi, K. Kodama, M. Ishikado, M. Nakamura,, R. Kajimoto, S. Shamoto
  • Organizer: Spectroscopies in Novel Superconductors 2019
  • Int'l Joint Research
• [Presentation] LSCO 系銅酸化物における磁気励起の構造の詳細 (2019)
  • Author(s): 池内和彦、菊池龍弥、中島健次、梶本亮一、脇本秀一、藤田全基
  • Organizer: 日本物理学会 2019 年秋季大会
• [Presentation] Detailed study of magnetic excitations in La1.75Sr0.25CuO4 (2019)
  • Author(s): K. Ikeuchi, T. Kikuchi, K. Nakajima, R. Kajimoto, S. Wakimoto, M. Fujita
  • Organizer: 3rd Asia-Oceania Conference on Neutron Scattering
  • Int'l Joint Research
• [Presentation] Al-impurity-induced magnetic excitations in heavily over-doped La1.7Sr0.3Cu0.95Al0.05O4 (2018)
  • Author(s): K. Ikeuchi, K. Nakajima, S. Ohira-Kawamura, R. Kajimoto, S. Wakimoto, K. Suzuki, and M. Fujita
  • Organizer: International Conference on Magnetism (ICM 2018) & International Conference on Strongly Correlated Electron Systems (SCES 2018)
  • Int'l Joint Research
• [Presentation] 鉄系超伝導体FeSeの(pi, pi)磁気励起 (2018)
  • Author(s): K. Ikeuchi, S. Shamoto, T. U. Ito, M. Ishikado, T. Watashige, S. Kasahara, R. Kajimoto, M. Nakamura, Lieh-Jeng Chang, T. Shibauchi, and Y. Matsuda
  • Organizer: 日本物理学会2018年秋季大会
• [Presentation] La1.75Sr0.25CuO4における磁気励起の構造の詳細 (2018)
  • Author(s): 池内和彦, 菊池龍弥, 中島健次, 梶本亮一, 脇本秀一, 藤田全基
  • Organizer: 第73回年次大会（2018年）
• [Presentation] Class structure of the low-energy magnetic excitations in over-doped La0.75Sr0.25CuO4 (2017)
  • Author(s): K. Ikeuchi, T. Kikuchi, K. Nakajima, R. Kajimoto, S. Wakimoto, M. Fujita
  • Organizer: International Conference on Strongly Correlated Electron Systems
  • Int'l Joint Research
• [Presentation] Fe-impurity-induced magnetic excitations in heavily over-doped La0.7Sr0.3Cu0.95Fe0.05O4 (2017)
  • Author(s): K. Ikeuchi, T. Kikuchi, K. Nakajima, R. Kajimoto, S. Wakimoto, M. Fujita
  • Organizer: International Conference on Low Temperature Physics
  • Int'l Joint Research
• [Presentation] La0.7Sr0.3Cu0.95Fe0.05O4におけるFe不純物誘起磁気励起 (2017)
  • Author(s): 池内和彦, 菊池龍弥, 中島健次, 梶本亮一, 脇本秀一, 藤田全基
  • Organizer: 日本物理学会2017年秋季大会