サイクロトロン共鳴による「隠れた秩序」相における電子構造の解明

2012 Fiscal Year Annual Research Report

• Project Area: Emergence of Heavy Electrons and Their Ordering
• Project/Area Number: 23102713
• Research Institution: Kyoto University
• Principal Investigator: 芝内 孝禎 京都大学, 理学(系)研究科(研究院), 准教授 (00251356)
• Project Period (FY): 2011-04-01 – 2013-03-31
• Keywords: 対称性の破れ / ネマティック秩序 / 磁場侵入長 / 量子臨界点

Outline of Annual Research Achievements

本研究では、重い電子系化合物の電子状態をマイクロ波を用いた低温測定により調べた。

1つめの成果として、URu2Si2の「隠れた秩序」相におけるフェルミ面の情報をサイクロトロン共鳴により明らかにした。磁場中の20-60GHz帯マイクロ波吸収測定においてサイクロトロン共鳴を観測し、26年間の謎であった「隠れた秩序」相のフェルミ面の主な構造の同定に成功した。ここで明らかになったのは、、最も信号の強い共鳴を与えるαバンドとよばれるホール面で、バンド計算や量子振動の測定からは明らかにされていなかった有効質量の分裂を発見し、[110]方向にホットスポットを持つことを強く示唆する結果を得た。この結果は、「隠れた秩序」相において正方晶の面内4回対称性を破る電子構造となっていることを示しており、「隠れた秩序」の理解が格段に進むことが期待される。
2つめはマイクロ波を用いた超伝導体の磁場侵入長測定を様々な強相関電子系において行った。特に重い電子系超伝導体の中でも反強磁性量子臨界点に近いことが知られているCeCoIn5およびCe2PdIn8の単結晶試料において、低温で磁場侵入長がともに温度の3/2乗に比例するという特異な振る舞いを示すことが明らかとなった。この温度依存性はこの系で期待されるｄ波超伝導の温度に比例する振る舞いとは異なっており、量子臨界性により超伝導電子の有効質量が波数空間に強く依存していることを示唆している。さらに同様な測定を鉄系超伝導体 BaFe2(As,P)2について行ったところ、量子臨界点近傍で同様な異常を示すとともに、絶対零度における磁場侵入長の値が鋭いピーク構造を持つことを明らかにした。この結果は、超伝導ドームの内部の絶対零度において臨界的な揺らぎが存在していることを実験的にはじめて直接示したものであり、反強磁性量子臨界点が超伝導状態内に存在することを示すものである。

Research Progress Status

24年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

24年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5 (2013)
  • Author(s): M. Scheffler, T. Weig, M. Dressel, H. Shishido, Y. Mizukami, T. Terashima, T. Shibauchi, and Y. Matsuda,
  • Journal Title: J. Phys. Soc. Jpn. Volume: 82 Pages: 043712
  • DOI: 10.7566/JPSJ.82.043712
  • Peer Reviewed
• [Journal Article] Disorder, Critical Currents, and Vortex Pinning Energies in Isovalently Substituted BaFe2(As1-xPx)2 (2013)
  • Author(s): S. Demirdis, Y. Fasano, S. Kasahara, T. Terashima, T. Shibauchi, Y. Matsuda, M. Konczykowski, H. Pastoriza, and C. J. van der Beek,
  • Journal Title: Phys. Rev. B Volume: 87 Pages: 094506
  • DOI: 10.1103/PhysRevB.87.094506
  • Peer Reviewed
• [Journal Article] Interplane Resistivity of Isovalent Doped BaFe2(As1-xPx)2 (2013)
  • Author(s): M. A. Tanatar, K. Hashimoto, S. Kasahara, T. Shibauchi, Y. Matsuda, and R. Prozorov,
  • Journal Title: Phys. Rev. B Volume: 87 Pages: 104506
  • DOI: 10.1103/PhysRevB.87.104506
  • Peer Reviewed
• [Journal Article] Anomalous Superfluid Density in Quantum Critical Superconductors (2013)
  • Author(s): K. Hashimoto, Y. Mizukami, R. Katsumata, H. Shishido, M. Yamashita, H. Ikeda, Y. Matsuda, J. A. Schlueter, J. D. Fletcher, A. Carrington, D. Gnida, D. Kaczorowski, and T. Shibauchi,
  • Journal Title: Proc. Natl. Acad. Sci. USA Volume: 110 Pages: 3293-3297
  • DOI: 10.1073/pnas.1221976110
  • Peer Reviewed
• [Journal Article] Strong Suppression of Superconductivity by Divalent Ytterbium Kondo-Holes in CeCoIn5 (2012)
  • Author(s): M. Shimozawa, T. Watashige, S. Yasumoto, Y. Mizukami, H. Shishido, S. K. Goh, T. Terashima, T. Shibauchi, and Y. Matsuda,
  • Journal Title: Phys. Rev. B Volume: 86 Pages: 144526
  • DOI: 10.1103/PhysRevB.86.144526
  • Peer Reviewed
• [Journal Article] Anomalous Upper Critical Field in CeCoIn5/YbCoIn5 Superlattices with Rashba-Type Heavy Fermion Interface (2012)
  • Author(s): S. K. Goh, Y. Mizukami, H. Shishido, D. Watanabe, S. Yasumoto, M. Shimozawa, M. Yamashita, T. Terashima, Y. Yanase, T. Shibauchi, A. I. Buzdin, and Y. Matsuda,
  • Journal Title: Phys. Rev. Lett. Volume: 105 Pages: 157006
  • DOI: 10.1103/PhysRevLett.109.157006
  • Peer Reviewed
• [Journal Article] Novel Pauli-Paramagnetic Quantum Phase in a Mott Insulator (2012)
  • Author(s): D. Watanabe, M. Yamashita, S. Tonegawa, Y. Oshima, H. M. Yamamoto, R. Kato, I. Sheikin, K. Behnia, T. Terashima, S. Uji, T. Shibauchi, and Y. Matsuda,
  • Journal Title: Nature Commun. Volume: 3 Pages: 1090
  • DOI: 10.1038/ncomms2082
  • Peer Reviewed
• [Journal Article] Thermodynamic Phase Diagram, Phase Competition, and Uniaxial Pressure Effects in BaFe2(As1-xPx)2 Studied by Thermal Expansion (2012)
  • Author(s): A. E. B#246;hmer, P. Burger, F. Hardy, T. Wolf, P. Schweiss, R. Fromknecht, H. v. L#246;hneysen, C. Meingast, H. K. Mak, R. Lortz, S. Kasahara, T. Terashima, T. Shibauchi, and Y. Matsuda,
  • Journal Title: Phys. Rev. B Volume: 86 Pages: 094521
  • DOI: 10.1103/PhysRevB.86.094521
  • Peer Reviewed
• [Journal Article] Octet-Line Node structure of Superconducting Order Parameter in KFe2As2 (2012)
  • Author(s): K. Okazaki, Y. Ota, Y. Kotani, et al.
  • Journal Title: Science Volume: 337 Pages: 1314-1317
  • DOI: 10.1126/science.1222793
  • Peer Reviewed
• [Journal Article] Cyclotron Resonance in the Hidden-Order Phase of URu2Si2 (2012)
  • Author(s): S. Tonegawa, K. Hashimoto, K. Ikada, Y. H. Lin, H. Shishido, Y. Haga, T. D. Matsuda, E. Yamamoto, Y. Onuki, H. Ikeda, Y. Matsuda, and T. Shibauchi,
  • Journal Title: Phys. Rev. Lett. Volume: 109 Pages: 036401
  • DOI: 10.1103/PhysRevLett.109.036401
  • Peer Reviewed
• [Journal Article] Measurement of an Energy Pseudogap for P-Doped and Co-Doped High-Temperature BaFe2As2 Superconductors Using Infrared Spectroscopy (2012)
  • Author(s): S. J. Moon, A. A. Schafgans, S. Kasahara, T. Shibauchi, T. Terashima, Y. Matsuda, M. A. Tanatar, R. Prozorov, A. Thaler, P. C. Canfield, A. S. Sefat, D. Mandrus, and D. N. Basov,
  • Journal Title: Phys. Rev. Lett. Volume: 109 Pages: 027006
  • DOI: 10.1103/PhysRevLett.109.027006
  • Peer Reviewed
• [Journal Article] A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in the Iron-Based Superconductor BaFe2(As1-xPx)2 (2012)
  • Author(s): K. Hashimoto, K. Cho, T. Shibauchi, et al.
  • Journal Title: Science Volume: 336 Pages: 1554-1557
  • DOI: 10.1126/science.1219821
  • Peer Reviewed
• [Journal Article] Electronic Nematicity above the Structural and Superconducting Transition in BaFe2(As1-xPx)2 (2012)
  • Author(s): S. Kasahara, H. J. Shi, K. Hashimoto, S. Tonegawa, Y. Mizukami, T. Shibauchi, K. Sugimoto, T. Fukuda, T. Terashima, A. H. Nevidomskyy, and Y. Matsuda,
  • Journal Title: Nature Volume: 486 Pages: 382-385
  • DOI: 10.1038/nature11178
  • Peer Reviewed
• [Journal Article] Emergent Rank-5 Nematic Order in URu2Si2 (2012)
  • Author(s): H. Ikeda, M.-T. Suzuki, R. Arita, T. Takimoto, T. Shibauchi, and Y. Matsuda,
  • Journal Title: Nature Phys. Volume: 8 Pages: 528-533
  • DOI: 10.1038/nphys2330
  • Peer Reviewed
• [Journal Article] Gradual Suppression of Antiferromagnetism in BaFe2(As1-xPx)2: Zero-Temperature Evidence for a Quantum Critical Point (2012)
  • Author(s): T. Iye, Y. Nakai, S. Kitagawa, K. Ishida, S. Kasahara, T. Shibauchi, Y. Matsuda, and T. Terashima,
  • Journal Title: Phys. Rev. B Volume: 85 Pages: 184505
  • DOI: 10.1103/PhysRevB.85.184505
  • Peer Reviewed
• [Presentation] 鉄系、銅系超伝導の実験 (2013)
  • Author(s): 芝内孝禎
  • Organizer: 日本物理学会第68回年次大会
  • Place of Presentation: 広島大学東広島キャンパス
  • Year and Date: 2013-03-26 – 2013-03-29
  • Invited
• [Presentation] Symmetry Breaking in the Hidden-Order Phase of URu2Si2 (2013)
  • Author(s): Takasada Shibauchi
  • Organizer: The March Meeting of the American Physical Society
  • Place of Presentation: Baltimore, MD, USA
  • Year and Date: 2013-03-18 – 2013-03-22
  • Invited
• [Presentation] Antiferromagnetic Quantum Critical Point and Nematic Transition in BaFe2(As1-xPx)2 (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: International Symposium on Superconductibity 2012 (ISS2012)
  • Place of Presentation: Funabori, Tokyo
  • Year and Date: 2012-12-03 – 2012-12-05
  • Invited
• [Presentation] Quantum Critical Phenomena in Strongly Correlated Electron Systems (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: Summit of Material Science 2012 (SMS2012)
  • Place of Presentation: Tohoku University, Sendai
  • Year and Date: 2012-11-28 – 2012-11-30
  • Invited
• [Presentation] 鉄ヒ素系超伝導体の隠れた量子臨界点とネマティック相転移 (2012)
  • Author(s): 芝内孝禎
  • Organizer: 日本物理学会秋季大会
  • Place of Presentation: 横浜国立大学
  • Year and Date: 2012-09-18 – 2012-09-21
  • Invited
• [Presentation] Exotic Superconductivity of Heavy Electrons in Artificial Two-Dimensional Kondo Lattices (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: International Conference on Quantum Criticality and Novel Phases (QCNP)
  • Place of Presentation: Dresden, Germany
  • Year and Date: 2012-08-27 – 2012-08-29
  • Invited
• [Presentation] Nematic Transition and Antiferromagnetic Quantum Critical Point in BaFe2(As,P)2 (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: Innovations in Strongly Correlated Electrons Workshop
  • Place of Presentation: Trieste, Italy
  • Year and Date: 2012-08-13 – 2012-08-17
  • Invited
• [Presentation] Nematic Transition and Antiferromagnetic Quantum Critical Point in BaFe2(As,P)2 (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: Second Joint Super‐PIRE REIMEI Workshop
  • Place of Presentation: Bethesda, MD, USA
  • Year and Date: 2012-08-03 – 2012-08-05
  • Invited
• [Presentation] Quantum Critical Point Hidden beneath the Superconducting Dome of BaFe2(As,P)2 (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: International Conference on Materials and Mechanisms of Superconductivity (M2S 2012)
  • Place of Presentation: Washington DC, USA
  • Year and Date: 2012-07-30 – 2012-08-03
  • Invited
• [Presentation] Exotic Superconductivity of Heavy Electrons in Artificial Two-Dimensional Kondo Lattices (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: The 19th International Conference on Magnetism (ICM2012) with Strongly Correlated Electron Systems (SCES)
  • Place of Presentation: Busan, Korea
  • Year and Date: 2012-07-08 – 2012-07-13
  • Invited
• [Presentation] Symmetry Breaking in the Hidden Order Phase of URu2Si2 (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: The 4th International Workshop on the Dual Nature of f-electrons
  • Place of Presentation: Himeji, Japan
  • Year and Date: 2012-07-04 – 2012-07-06
  • Invited
• [Presentation] Exotic Superconductivity of Heavy Electrons in Artificial Two-Dimensional Kondo Lattices (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: Collaborative Conference on Materials Research (CCMR2012)
  • Place of Presentation: Seoul, Korea
  • Year and Date: 2012-06-25 – 2012-06-29
  • Invited
• [Presentation] BaFe2(As1-xPx)2の超伝導ドーム内に隠れた量子臨界点 (2012)
  • Author(s): 芝内孝禎
  • Organizer: 基研研究会「鉄系高温超伝導の物理 ～スピン・軌道・格子～」
  • Place of Presentation: 京都大学基礎物理学研究所
  • Year and Date: 2012-06-21 – 2012-06-21
  • Invited
• [Presentation] Symmetry Breaking in the Hidden Order Phase of URu2Si2 (2012)
  • Author(s): Takasada Shibauchi
  • Organizer: International Conference on Superconductivity and Magnetism (ICSM2012)
  • Place of Presentation: Istanbul, Turkey
  • Year and Date: 2012-04-29 – 2012-05-04
  • Invited
• [Remarks] Research Highlights
  • URL: http://kotai2.scphys.kyoto-u.ac.jp/index.php?Research%20Highlights
• [Remarks] 絶対零度の量子ゆらぎにより重くなる超伝導電子－電子が特定の方向で重くなる異常な現象を発見－
  • URL: http://www.kyoto-u.ac.jp/ja/news_data/h/h1/news6/2012/130212_1.htm
• [Remarks] 超伝導物質が絶対零度で示す新しい臨界現象を発見
  • URL: http://www.kyoto-u.ac.jp/ja/news_data/h/h1/news6/2012/120622_2.htm
• [Remarks] 鉄原子を含む高温超伝導体の仕組みを解くカギ「電子のネマティック液晶状態」を発見
  • URL: http://www.kyoto-u.ac.jp/ja/news_data/h/h1/news6/2012/120621_1.htm