Novel Quantum Liquids in Strongly Correlated Electrons

2008 Fiscal Year Final Research Report

• Project/Area Number: 18684020
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics II
• Research Institution: The University of Tokyo
• Principal Investigator: NAKATSUJI Satoru The University of Tokyo, 物性研究所, 准教授 (70362431)
• Project Period (FY): 2006 – 2008
• Keywords: 非フェルミ液体 / 超伝導 / スピン液体 / スピングラス

Research Abstract

新しい量子液体として超伝導、非フェルミ液体、スピン液体を取り上げ、以下の研究を行ってきた。
(1)新物質β-YbA1B_4を開発し、純良単結晶の育成に成功し、この物質がYb化合物の重い電子系として初の超伝導体であり、転移点直上で明瞭な非フェルミ液体性を示すことを明らかにした。超伝導特性からスピン揺らぎによる異方的超伝導が示唆される。
(2)三角格子磁性体NiGa_2S_4については自らの物質合成と物性測定、共同研究によるNMR,μSR実験から10Kでの明確な相転移を経て低温でMHz程度の揺らぎをもつ粘性の高いスピン液体状態が形成される可能性を見出した。2K以下のスピン凍結状態で現れる比熱のT^2則が不純物スピンサイズの偶奇性に依存することを発見した。これは比熱のコヒーレントな振る舞いに対する量子揺らぎの重要性を示唆する。

Research Products

• [Journal Article] High-field electron spin resonance in the two-dimensional triangular-lattice antiferromagnet NiGa_2S_4 (2008)
  • Author(s): H. Yamaguchi, S. Kimura, M. Hagiwara, Y. Nambu, S. Nakatsuji, Y. Maeno, K. Kindo
  • Journal Title: Physical Review B Volume 78 Pages: 180404(R)/1-4
  • Peer Reviewed
• [Journal Article] Unconventional spin freezing and fluctuations in the frustrated antiferromagnet NiGa_2S_4 (2008)
  • Author(s): D. E. MacLaughlin, Y. Nambu, S. Nakatsuji, R. H. Heffner, Lei Shu, O. O. Bernal, K. Ishida
  • Journal Title: Physical Review B Volume 78 Pages: 220403(R)/1-4
  • Peer Reviewed
• [Journal Article] Spin dependent impurity effects in the 2D frustrated magnetism of NiGa_2S_4 (2008)
  • Author(s): Y. Nambu, S. Nakatsuji, Y. Maeno, E. K. Okudzeto, J. Y. Chan
  • Journal Title: Physical Review Letters Volume 101 Pages: 207204/1-4
  • Peer Reviewed
• [Journal Article] Superconducting properties of the non-Fermi-liquid system β-YbA1B_4 (2008)
  • Author(s): K. Kuga, Y. Karaki, Y. Matsumoto, Y. Machida, S. Nakatsuji
  • Journal Title: Physical Review Letters Volume 101 Pages: 137004/1-41
• [Journal Article] Superconductivity and quantum criticality in the heavy-fermion system β-YbA1B_4 (2008)
  • Author(s): S. Nakatsuji, K. Kuga, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, E. Pearson, G. G. Lonzarich, H. Lee, L. Balicas, Z. Fisk
  • Journal Title: Nature Physics Volume4 Pages: 603-607
  • Peer Reviewed
• [Journal Article] Synthesis and characterization of the quasi-two-dimensional triangular antiferromagnets Ni_<1-x>M_xGa_2S_4 (M=Mn, Fe, Co, Zn) (2008)
  • Author(s): Y. Nambu, M. Ichihara, Y. Kiuchi, S. Nakatsuji, Y. Maeno
  • Journal Title: ournal of Crystal Growth Volume310 Pages: 1881-1885
  • Peer Reviewed
• [Journal Article] Spin dynamics and spin freezing behavior in the two-dimensional antiferromagnet NiGa_2S_4 revealed by Ga-NMR, NQR and mu SR measurements (2008)
  • Author(s): Hideo Takeya, Kenji Ishida, Kentaro Kitagawa, Yoshihiko Ihara, Keisuke Onuma, Yoshiteru Maeno, Yusuke Nambu, Satoru Nakatsuji, Douglas E. MacLaughlin, Akihiko Koda, Ryosuke Kadono
  • Journal Title: Physical Review B Volume77 Pages: 054429/1-13
  • Peer Reviewed
• [Journal Article] Spin Disorder and Order in Quasi-2D Triangular Heisenberg Antiferromagnets: Comparative Study of FeGa_2S_4, Fe_2Ga_2S_5, and NiGa_2S_4 (2007)
  • Author(s): S. Nakatsuji, H. Tonomura, K. Onuma, Y. Nambu, O. Sakai, Y. Maeno, R. T. Macaluso, Julia Y. Chan
  • Journal Title: Physcial Review Letters Volume99 Pages: 157203/1-4
  • Peer Reviewed
• [Journal Article] Unusual Superexchange Pathways in an NiS_2 Triangular Lattice with Negative Charge-Transfer Energy (2007)
  • Author(s): K. Takubo, T. Mizokawa, J.-Y. Son, Y. Nambu, S. Nakatsuji, Y. Maeno
  • Journal Title: Physcial Review Letters Volume99 Pages: 037203/1-4
  • Peer Reviewed
• [Journal Article] Crystal Structure and Physical Properties of a New Polymorph of LnA1B_4 (Ln=Yb, Lu) (2007)
  • Author(s): Robin T. Macaluso, Satoru Nakatsuji, Kentaro Kuga, Evan Lyle Thomas, Yo Machida, Yoshiteru Maeno, Zachary Fisk, Julia Y. Chan
  • Journal Title: Chemistry of Materials Volume19 Pages: 1918-1922
  • Peer Reviewed
• [Presentation] Quantum Criticality and Superconductivity of the Heavy Fermion System β-YbA1B_4 (2009)
  • Author(s): Satoru Nakatsuji
  • Organizer: American Physical Society March Meeting, Symposium on New Aspect of Heavy Fermion Superconductors
  • Place of Presentation: Pittsburg, USA
  • Year and Date: 2009-03-17
• [Presentation] Superconductivity and Non-Fermi-Liquid Behavior in β-YbA1B_4 (2008)
  • Author(s): Satoru Nakatsuji
  • Organizer: International Conference on Strongly Correlated Electron Systems
  • Place of Presentation: Buzios/Rio, Brazil
  • Year and Date: 2008-08-18
• [Presentation] Geometrical Frustration Effects in Phase transition and Transport Phenomena (2008)
  • Author(s): Satoru Nakatsuji
  • Organizer: Highly Frustrated Magnetism 2008
  • Place of Presentation: Braunschweig, Germany
  • Year and Date: 2008-08-09
• [Presentation] Exotic Freezing Phenomena in Metallic and Insulating Frustrated Magnets (2008)
  • Author(s): Satoru Nakatsuji
  • Organizer: International Workshop "Topological Aspects of Solid State Physics"
  • Place of Presentation: ISSP, Univ. of Tokyo
  • Year and Date: 2008-06-20
• [Presentation] Unconventional Spin Freezing and Transport phenomena due to Geometrical Frustration (2007)
  • Author(s): Satoru Nakatsuji
  • Organizer: KIAS Workshop on "Quantum Magnetism"
  • Place of Presentation: Seoul, Korea
  • Year and Date: 2007-12-18
• [Presentation] Spin Disordered States in Geometrically Frustrated Lattices (2007)
  • Author(s): Satoru Nakatsuji
  • Organizer: International conference of crystal growth 15
  • Place of Presentation: Salt Lake City, Utah, USA
  • Year and Date: 2007-08-14
• [Patent(Industrial Property Rights)] 工業所有権の名称:β-YbA1B_4を有してなる磁気冷凍作業物質及びその製造方法、並びにそれを用いた磁気冷凍方法及び磁気冷凍装置 (2007)
  • Inventor(s): 中辻知, 榊原俊郎, 前野悦輝
  • Industrial Property Rights Holder: 前野悦輝
  • Industrial Property Number: 特願2007-094705
  • Filing Date: 2007-03-30