Fabrication of Heavy Fermion Superlattices

2017 Fiscal Year Annual Research Report

• Project/Area Number: 25220710
• Research Institution: Kyoto University
• Principal Investigator: 松田 祐司 京都大学, 理学研究科, 教授 (50199816)
• Co-Investigator(Kenkyū-buntansha): 芝内 孝禎 東京大学, 大学院新領域創成科学研究科, 教授 (00251356) ; 笠原 成 京都大学, 理学研究科, 助教 (10425556) ; 花栗 哲郎 国立研究開発法人理化学研究所, その他, 研究員 (40251326) ; 寺嶋 孝仁 京都大学, 理学研究科, 教授 (40252506)
• Project Period (FY): 2013-05-31 – 2018-03-31
• Keywords: 鉄系高温超伝導 / 銅酸化物高温超伝導 / 重い電子系 / 量子臨界点 / 超伝導対称性 / トンネル顕微鏡 / 人工超格子 / 非従来型超伝導

Outline of Annual Research Achievements

本年度は、鉄系超伝導体特に最も単純な結晶構造を持つFeSeに関する研究、重い電子系超伝導体、特に人工超格子、超伝導対称性とトンネル顕微鏡による電子錠遺体の直接観測の研究、銅酸化物高温超伝導体における擬ギャップの研究を主として行った。
FeSe系化合物に関しては、まず超伝導状態においてフェルミエネルギーに対する超伝導ギャップエネルギーの比が従来のいかなる超伝導体よりも大きいこと明らかにし、この系がボーズ・アインシュタイン凝縮状態に最も近い超伝導体であることを示した。さらにSドープにより構造相転移が抑制され、いわゆるネマティック量子臨界点を持つことを示し、この点を境に超伝導対称性が大きく変化することを示した。
重い電子系超伝導体の研究では、CeCoIn5/CeRhIn5の人工超格子を作製し、d波超伝導とスピン密度波が空間的に共存する系を創成した。さらに圧力をかけることにより、インターフェイスを通じて磁気揺らぎと超伝導が相互作用しうることを示した。CeCu2Si2は最も古いも遺伝子型超伝導体であるが、磁気臨界点の近くにあるため長い間、d波超伝導が実現すると考えられてきた。我々は純良単結晶を用いた様々な測定により、この系がS波超伝導対称性を持つことを示した。CeCoIn5薄膜においてトンネル顕微鏡を用いた電子状態の直接観測に成功した。これは重い電子系超伝導体では初めてである。特にZn不純物まわりの電子状態を観測し、これまでの研究で予想されてきた不純物周りの局所的な磁気ドロプレットは生じていないことを明らかにした。
銅酸化物高温超伝導体における最大の謎は、アンダードープ領域における擬ギャップの形成である。我々はYBCOに対し、超高感度の磁気トルク測定を行い、擬ギャップ温度で回転対称性の破れたネマティック相転移が生じていることを解明した。

Research Progress Status

29年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

29年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] Hochfeld-Magnetlabor Dresden/Karlsruhe Institute of Technology/MaxPlanck Institute(Germany)
  • Country Name: Germany
  • Counterpart Institution: Hochfeld-Magnetlabor Dresden/Karlsruhe Institute of Technology/MaxPlanck Institute
  • # of Other Institutions: 1
• [Int'l Joint Research] University of Bristol(United Kingdom)
  • Country Name: United Kingdom
  • Counterpart Institution: University of Bristol
• [Int'l Joint Research] Ecole Polytechnique(France)
  • Country Name: France
  • Counterpart Institution: Ecole Polytechnique
• [Int'l Joint Research] KAIST(韓国)
  • Country Name: KOREA (REP. OF KOREA)
  • Counterpart Institution: KAIST
• [Int'l Joint Research] Los Alamos National Loboratory(米国)
  • Country Name: U.S.A.
  • Counterpart Institution: Los Alamos National Loboratory
• [Int'l Joint Research]
  • # of Other Countries: 2
• [Journal Article] Superconducting Gap Anisotropy Sensitive to Nematic Domains in FeSe (2018)
  • Author(s): T. Hashimoto, Y. Ota, H. Q. Yamamoto, Y. Suzuki, T. Shimojima, S. Watanabe, C. Chen, S. Kasahara, Y. Matsuda, T. Shibauchi, K. Okazaki, and S. Shin
  • Journal Title: Nature Commun. Volume: 9 Pages: 282
  • DOI: 10.1038/s41467-017-02739-y
  • Peer Reviewed / Open Access
• [Journal Article] Abrupt change of the superconducting gap structure at the nematic critical point in FeSe1-xSx (2018)
  • Author(s): Y. Sato, S. Kasahara, T. Taniguchi, X.Z. Xing, Y. Kasahara, Y. Tokiwa, Y. Yamakawa, H. Kontani, T. Shibauchi, and Y. Matsuda
  • Journal Title: Proc. Natl. Acad. Sci. USA Volume: 115 Pages: 1227-1231
  • DOI: 10.1073/pnas.1717331115
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] In Situ STM Observation of Nonmagnetic Impurity Effect in MBE-grown CeCoIn5 Films (2018)
  • Author(s): M. Haze, Y. Torii, R. Peters, S. Kasahara, Y. Kasahara, T. Shibauchi, T. Terashima, and Y. Matsuda
  • Journal Title: J. Phys. Soc. Jpn. 87 Volume: 87 Pages: 034702
  • DOI: 10.7566/JPSJ.87.034702
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Tuning the pairing interaction in a d-wave superconductor by paramagnons injected through interfaces (2018)
  • Author(s): M. Naritsuka, P.F.S. Rosa, Yongkang Luo, Y. Kasahara, Y.Tokiwa, T. Ishii, S. Miyake, T.Terashima, T. Shibauchi, F. Ronning, J.D. Thompson, and Y. Matsuda
  • Journal Title: Phys. Rev. Lett. Volume: 印刷中 Pages: -
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Unusual thermal Hall eect in a Kitaev spin liquid candidate RuCl3 (2018)
  • Author(s): Y. Kasahara, K. Sugii, T. Ohnishi, M. Shimozawa, M. Yamashita, N. Kurita, H. Tanaka, J. Nasu, Y. Motome, T. Shibauchi, and Y. Matsuda
  • Journal Title: Phys.Rev. Lett. Volume: 印刷中 Pages: -
  • Peer Reviewed
• [Journal Article] Two distinct superconducting pairing states divided by the nematic end point in FeSe1-xSx (2018)
  • Author(s): T. Hanaguri, K. Iwaya, Y. Kohsaka, T. Machida, T. Watashige, S. Kasahara, T. Shibauchi, and Y. Matsuda
  • Journal Title: Science Adv. Volume: 印刷中 Pages: -
• [Journal Article] Majorana quantization and half-integer thermal quantum Hall effect in a Kitaev spin liquid (2018)
  • Author(s): Y. Kasahara, T. Ohnishi, Y. Mizumaki, O.Tanaka, Sixiao Ma, K. Sugii, N. Kurita, H.Tanaka, J. Nasu, Y. Motome, T. Shibauchi, and Y. Matsuda
  • Journal Title: Nature Volume: 印刷中 Pages: -
  • Peer Reviewed
• [Journal Article] Quasiparticle Excitations in the Superconducting State of FeSe Probed by Thermal Hall Conductivity in the Vicinity of the BCS-BEC Crossover (2017)
  • Author(s): T. Watashige, S. Arsenijevi, T. Yamashita, D. Terazawa, T. Onishi, L. Opherden, S. Kasahara, Y. Tokiwa, Y. Kasahara, T. Shibauchi, H. v. Loehneysen, J. Wosnitza, and Y. Matsuda
  • Journal Title: J. Phys. Soc. Jpn. Volume: 86 Pages: 014707
  • DOI: 10.7566/JPSJ.86.014707
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu2Si2 (2017)
  • Author(s): T. Yamashita, T. Takenaka, Y. Tokiwa, J. A. Wilcox, Y. Mizukami, D. Terazawa, Y. Kasahara, S. Kittaka, T. Sakakibara, M. Konczykowski, S. Seiro, H. S. Jeevan, C. Geibel, C. Putzke, T. Onishi, H. Ikeda, A. Carrington, T. Shibauchi, Y. Matsuda
  • Journal Title: Science Advances Volume: 3 Pages: e1601667
  • DOI: 10.1126/sciadv.1601667
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Impact of Disorder on the Superconducting Phase Diagram in BaFe2(As1-xPx)2 (2017)
  • Author(s): Y. Mizukami, M. Konczykowski, K. Matsuura, T. Watashige, S. Kasahara, Y. Matsuda, and T. Shibauchi
  • Journal Title: J. Phys. Soc. Jpn. Volume: 86 Pages: 083706
  • DOI: 10.7566/JPSJ.86.083706
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Thermodynamic evidence for a nematic phase transition at the onset of the pseudogap in YBa2Cu3Oy (2017)
  • Author(s): Y. Sato, S. Kasahara, H. Murayama, Y. Kasahara, E.-G. Moon, T. Nishizaki,T. Loew, J. Porras, B. Keimer, T. Shibauchi and Y. Matsuda
  • Journal Title: Nature Phys. Volume: 13 Pages: 1074-1078
  • DOI: 10.1038/nphys4205
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion CeCu2Si2 (2017)
  • Author(s): T. Takenaka, Y. Mizukami, J. A. Wilcox, M. Konczykowski, S. Seiro, C. Geibel, Y. Tokiwa, Y. Kasahara, C. Putzke, Y. Matsuda, A. Carrington, and T. Shibauchi
  • Journal Title: Phys. Rev. Lett. Volume: 119 Pages: 077001
  • DOI: 10.1103/PhysRevLett.119.077001
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Magnetic and Superconducting Properties of the Heavy-Fermion CeCoIn5 Epitaxial Thin Film Probed by Nuclear Quadrupole Resonance (2017)
  • Author(s): T. Yamanaka, M. Shimozawa, H. Shishido, S. Kitagawa, H. Ikeda, T. Shibauchi, T. Terashima, Y. Matsuda, and K. Ishida
  • Journal Title: Phys. Rev. B Volume: 96 Pages: 060507
  • DOI: 10.1103/PhysRevB.96.060507
  • Peer Reviewed
• [Journal Article] Maximizing Tc by Tuning Nematicity and Magnetism in FeSe1-xSx Superconductors (2017)
  • Author(s): K. Matsuura, Y. Mizukami, Y. Arai, Y. Sugimura, N. Maejima, A. Machida, T. Watanuki, T. Fukuda, T. Yajima, Z. Hiroi, K. Y. Yip, Y. C. Chan, Q. Niu, S. Hosoi, K. Ishida, K. Mukasa, S. Kasahara, J.-G. Cheng, S. K. Goh, Y. Matsuda, Y. Uwatoko, and T. Shibauchi
  • Journal Title: Nature Commun. Volume: 8 Pages: 1143
  • DOI: 10.1038/s41467-017-01277-x
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Emergent Exotic Superconductivity in Artificially Engineered Tricolor Kondo Superlattices (2017)
  • Author(s): M. Naritsuka, T. Ishii, S. Miyake, Y. Tokiwa, R. Toda, M. Shimozawa, T. Terashima, T. Shibauchi, Y. Matsuda, and Y. Kasahara
  • Journal Title: Phys. Rev. B Volume: 96 Pages: 174512
  • DOI: 10.1103/PhysRevB.96.174512
  • Peer Reviewed
• [Presentation] Majorana fermions in Kitaev quantum spin liquid (2018)
  • Author(s): Yuji Matsuda
  • Organizer: Topological Magnets and Topological SUperconductors
  • Int'l Joint Research / Invited
• [Presentation] Thermodynamic evidence for a nematic phase transition at the onset of pseudogap in YBa2Cu3O6+d and HgBa2CuO4+d (2018)
  • Author(s): Yuji Matsuda
  • Organizer: American Physical Society March Meeting
  • Int'l Joint Research / Invited
• [Presentation] Emergent quasiparticles in quantum spin liquids (2018)
  • Author(s): Yuji Matsuda
  • Organizer: Annual meeting, the Physical Society of Japan
• [Presentation] Monopoles and Photon in quantum spin ice (2017)
  • Author(s): Yuji Matsuda
  • Organizer: International Workshop on Quantum Spin Ice
  • Int'l Joint Research / Invited
• [Presentation] Exotic superconductivity in FeSe (2017)
  • Author(s): Yuji Matsuda
  • Organizer: The 3rd Conference on Condensed Matter Physics
  • Int'l Joint Research / Invited
• [Presentation] Fully gapped superconductivity with no sign change in CeCu2SI2 (2017)
  • Author(s): Yuji Matsuda
  • Organizer: Korean Physical Society Meeting
  • Int'l Joint Research / Invited
• [Presentation] Thermodynamic evidence for a nematic phase transition at the onset of pseudogap in YBa2Cu3O6+d and HgBa2CuO4+d (2017)
  • Author(s): Yuji Matsuda
  • Organizer: Order, Fluctuations, and Strong Correlations: New Platforms and Developments
  • Int'l Joint Research / Invited
• [Presentation] BCS-BEC crossover and exotic superconducting pairing in FeSe (2017)
  • Author(s): Yuji Matsuda
  • Organizer: the 28th International Conference on Low Temperature Physics
  • Int'l Joint Research / Invited
• [Presentation] Emergent exotic quasiparticles in frustrated quantum magnets (2017)
  • Author(s): Yuji Matsuda
  • Organizer: Kanamori Memorial Symposium
  • Int'l Joint Research / Invited
• [Presentation] Majorana quantization (2017)
  • Author(s): Yuji Matsuda
  • Organizer: Conference on Topological Phases and Topological Quantum Computation
  • Int'l Joint Research / Invited