精密トルク測定による電子ネマティック相の研究

2012 Fiscal Year Annual Research Report

• Project/Area Number: 23654119
• 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)
• Keywords: 対称性の破れ / 磁気トルク / 角度依存性 / 斜方晶歪み / ネマティック秩序

Research Abstract

成果として、微小カンチレバーを用いた磁気トルクの角度依存性測定システムを完成させ、鉄系超伝導体BaFe2(As,P)2の微小単結晶試料において角度依存性の温度変化の測定により、電子ネマティック相転移を見出すことに成功した。具体的には、転移温度が最大の超伝導を示す最適組成の試料において、転移温度30 Kよりはるかに高温の80 K程度からトルクの面内角度依存性に明確な2回対称性成分を観測した。このような2回対称成分は、4回対称性をもつ正方晶の物質では通常期待されない振る舞いであり、電子系の対称性が方向性を示すネマティック状態となっていることを示す強い証拠である。これまで、鉄系超伝導体では、結晶構造が正方晶から斜方晶へと構造相転移することが、低置換の組成領域で報告されているが、この構造相転移は最適組成領域では見られなかった。さらに様々な組成について同様の測定を行ったところ、構造相転移温度よりも高温でトルクの2回対称性が現れることが明らかとなった。また、その転移温度はP置換とともに系統的に低温へ向かってシフトしていき、超伝導ドームを覆うように高置換領域まで延びていることがあきらかとなった。さらにその磁場依存性測定により、電子ネマティック状態は磁場によって誘起されたものではなく、ゼロ磁場でも対称性を自発的に破る状態となっていることを強く示唆する結果を得ている。また同様の測定を電子ドープ系のBa(Fe,Co)2As2について行ったところ、同様の2回対称性が現れることを見出し、その転移温度のドープ量依存性はP置換系と同様に超伝導ドームを覆うような相図が得られた。これらの結果は、鉄系超伝導体の相図上において、構造相転移とは別に電子系のネマティック相転移線がより高温に存在するという、新たな情報を与えるものであり、鉄系超伝導の発現機構を議論する上で重要な結果であると考えられる。

Research Products

• [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: DOI:10.1073/pnas.1221976110
  • Peer Reviewed
• [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] 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: doi:10.1038/ncomms2082
  • 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] Thermodynamic Phase Diagram, Phase Competition, and Uniaxial Pressure Effects in BaFe2(As1-xPx)2 Studied by Thermal Expansion (2012)
  • Author(s): A. E. Böhmer, P. Burger, F. Hardy, T. Wolf, P. Schweiss, R. Fromknecht, H. v. Löhneysen, 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] 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: 20130318-20130322
  • Invited
• [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: 2013-03-28
• [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: 20121203-20121205
  • 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: 20121128-20121130
  • 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: 20120813-20120817
  • 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: 20120803-20120805
  • 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: 20120730-20120803
  • 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: 20120704-20120706
  • 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: 20120625-20120629
  • 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: 20120621-20120622
  • 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: 20120429-20120504
  • 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: 2012-09-19
• [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: 2012-08-29
• [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: 2012-07-11
• [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