2000 年度実績報告書

強相関電子系における量子相転移

研究課題

研究課題/領域番号	11694074
研究機関	京都大学
研究代表者	SIGRIST Manfred W. 京都大学, 基礎物理学研究所, 教授 (60293966)
研究分担者	常次宏一筑波大学, 物質工学系, 助教授 (80197748) 川上則雄大阪大学, 大学院・工学研究科, 教授 (10169683) 上田和夫東京大学, 物性研究所, 教授 (70114395) 古川信夫青山学院大学, 理工学部, 助教授 (00238669) 古崎昭京都大学, 基礎物理学研究所, 助教授 (10238678)
キーワード	量子相転移 / 強相関電子系 / 磁性 / スピンギャップ / ランダムスピン系 / 近藤格子 / 異方的超伝導 / 非磁性不純物
研究概要	平成12年度の研究実績は以下のとおりである。 1)ダイマー状態、プラケットRVB状態、そして混合スピン構造をもった量子スピン系における量子相転移を、valence-bond solid状態と種々の磁気秩序相との間の相転移に着目して、解析した。 2)秩序相と無秩序相の間の量子相転移に対する非磁性不純物の影響を、プラケットRVB状態やダイマー状態をもつスピン1/2の量子スピン系について研究した。 3)CaをドープしたSr_2RuO_4について、3種類のd電子軌道がフェルミ面に寄与していることの効果を研究し、一種の部分的なMott転移により局在したスピンや軌道の自由度が生じていることを明らかにした。 4)パイロクロア格子上のスピン系の基底状態と低エネルギーでの物性を解析し、大きな残留エントロピーにより引き起こされる量子相転移を議論した。 5)二重交換模型における量子相転移を調べるため、量子モンテカルロ計算を行ない、転移の臨界指数を数値的に評価した。 6)Mott転移近傍の銅酸化物のフェルミ面の形状変化(切断)に対するウムクラップ散乱の影響を、弱結合の繰り込み群の手法により解析した。 7)非対角の乱れをもった準一次元系(量子細線)における低エネルギー準粒子の状態密度やアンダーソン局在の問題を調べ、種々のユニバーサリティクラスについて特徴的な量子効果を明らかにした。 8)d波超伝導体の表面で起こる相転移について研究し、磁気的秩序をもった超伝導状態と時間反転対称性の破れた超伝導状態の間の競合について議論した。

研究成果
(24件)

すべてその他

すべて文献書誌 (24件)

[文献書誌] S.Miyahara and K.Ueda: "Supersturctures at Magnetization Plateaus in SrCu_2(BO_3)_2"Physical Review B. 60. 3417-3424 (2000)
[文献書誌] Y.Yamashita,N.Shibata and K.Ueda: "Numerical Study of the One-Dimensional Spin-Orbit Coupled System with SU(2)【cross product】SU(2) Symmetry"Journal of the Physical Society of Japan. 69. 242-247 (2000)
[文献書誌] K.Ueda and S.Miyahara: "Orthogonal Dimer Ground State and its Excitations"Journal of the Physical Society of Japan : Supplement B. 69. 326-331 (2000)
[文献書誌] S.Miyahara and K.Ueda: "The magnetization plateaus of SrCu_2(BO_3)_2"Physica B. 281&282. 661-662 (2000)
[文献書誌] A.Koga and N.Kawakami: "Quantum Phase Transitions for Mixed Spin Systems"Journal of the Physical Society of Japan : Supplement A. 69. 319-325 (2000)
[文献書誌] Y.Yamashita,N.Shibata and K.Ueda: "Crossover Phenomena in the One-dimensional SU(4) Spin-Orbit Model under Magnetic Fields"Physical Review B. 61. 4012-4018 (2000)
[文献書誌] Y.Tsukamoto,N.Kawakami,Y.Yamashita and K.Ueda: "Gap Formation for the One-dimensional SU(4) Spin-Orbital Model"Physica B. 281&282. 540-541 (2000)
[文献書誌] Y.Yamashita,N.Shibata and K.Ueda: "Lower Symmetric Generalization of the SU(4) Spin-Orbit Model"Physica B. 281&282. 542-543 (2000)
[文献書誌] Y.Yamashita and K.Ueda: "Spin Driven Jahn-Teller Distortion in a Pyrochlore System"Physical Review Letters. 85. 4960-4963 (2000)
[文献書誌] M.Oshikawa,K.Ueda,H.Aoki,A.,Ochiai and M.Koghi: "Field-Induced Gap Formation in Yb_4As_3"Journal of the Physical Society of Japan. 68. 3181-3184 (1999)
[文献書誌] H.Aoki,A.Ochiai,M.Oshikawa and K.Ueda: "Magnetic Anisotropy in Yb_4As_3 with One-dimensional Yb^<3+> Chains"Physica B. 281&282. 465-467 (2000)
[文献書誌] T.Akimoto,Y.Moritomo,A.Nakamura and N.Furukawa: "Observation of Anomalous Single-Magnon Scattering in Half-Metallic Ferromagnets by Chemical Pressure Control"Physical Review Letters. 85. 3914-3917 (2000)
[文献書誌] Y.Motome and N.Furukawa: "Critical Temperature of Ferromagnetic Transition in Three-Dimensional Double-Exchange Models"Journal of the Physical Society of Japan. 69. 3785-3788 (2000)
[文献書誌] N.Furukawa: "Unconventional One-Magnon Scattering Resistivity in Half-Metals"Journal of the Physical Society of Japan. 69. 1954-1957 (2000)
[文献書誌] T.Moriya and K.Ueda: "Spin Fluctuations and High-Temperature Superconducticity"Advances in Physics. 49. 555-606 (2000)
[文献書誌] H.Kontani,K.Kanki and K.Ueda: "Anomalous Behaviors of the Transport Phenomena in High-T_c Superconductors"Physica B. 281&282. 808-809 (2000)
[文献書誌] M.Sigrist et al.: "The Chiral p-Wave State in Sr_2RuO_4"Journal of the Physical Society of Japan : Supplement B. 69. 127-132 (2000)
[文献書誌] T.Morinari and M.Sigrist: "The Influence of Chiral Surface States on the London Penetration Depth in Sr_2RuO_4"Journal of the Physical Society of Japan. 69. 2411-2414 (2000)
[文献書誌] C.Honerkamp,K.Wakabayashi and M.Sigrist: "Instabilities at [110]-Surfaces of d_<x^2-y^2>-Wave Superconductors"Europhysics Letters. 50. 368-375 (2000)
[文献書誌] P.W.Brouwer,C.Mudry and A.Furusaki: "Nonuniversality in Quantum Wires with Off-Diagonal Disorder : A Geometric Point of View"Nuclear Physics B. 565. 653-663 (2000)
[文献書誌] P.W.Brouwer,C.Mudry and A.Furusaki: "Density of States in Coupled Chains with Off-Diagonal Disorder"Physical Review Letters. 84. 2913-2916 (2000)
[文献書誌] Y.Maeno,T.M.Rice and M.Sigrist: "The Intriguing Superconductivity of Strontium Ruthenate"Physics Today. 54,1. 42-47 (2001)
[文献書誌] S.Wessel,B.Normand,M.Sigrist and S.Haas: "Order by Disorder from Non-magnetic Impurities in a Two-dimensional Quantum Spin Liquid"Physical Review Letters. 86. 1086-1089 (2001)
[文献書誌] C.Honerkamp,M.Salmhofer,N.Furukawa and T.M.Rice: "Breakdown of the Landau-Fermi Liquid in Two Dimensions due to Umklapp Scattering"Physical Review B. 63. 035109-1,03510* (2001)

2000 年度 実績報告書

強相関電子系における量子相転移

研究代表者

SIGRIST Manfred W. 京都大学, 基礎物理学研究所, 教授 (60293966)

研究成果

[文献書誌] S.Miyahara and K.Ueda: "Supersturctures at Magnetization Plateaus in SrCu_2(BO_3)_2"Physical Review B. 60. 3417-3424 (2000)

[文献書誌] Y.Yamashita,N.Shibata and K.Ueda: "Numerical Study of the One-Dimensional Spin-Orbit Coupled System with SU(2)【cross product】SU(2) Symmetry"Journal of the Physical Society of Japan. 69. 242-247 (2000)

[文献書誌] K.Ueda and S.Miyahara: "Orthogonal Dimer Ground State and its Excitations"Journal of the Physical Society of Japan : Supplement B. 69. 326-331 (2000)

[文献書誌] S.Miyahara and K.Ueda: "The magnetization plateaus of SrCu_2(BO_3)_2"Physica B. 281&282. 661-662 (2000)

[文献書誌] A.Koga and N.Kawakami: "Quantum Phase Transitions for Mixed Spin Systems"Journal of the Physical Society of Japan : Supplement A. 69. 319-325 (2000)

[文献書誌] Y.Yamashita,N.Shibata and K.Ueda: "Crossover Phenomena in the One-dimensional SU(4) Spin-Orbit Model under Magnetic Fields"Physical Review B. 61. 4012-4018 (2000)

[文献書誌] Y.Tsukamoto,N.Kawakami,Y.Yamashita and K.Ueda: "Gap Formation for the One-dimensional SU(4) Spin-Orbital Model"Physica B. 281&282. 540-541 (2000)

[文献書誌] Y.Yamashita,N.Shibata and K.Ueda: "Lower Symmetric Generalization of the SU(4) Spin-Orbit Model"Physica B. 281&282. 542-543 (2000)

[文献書誌] Y.Yamashita and K.Ueda: "Spin Driven Jahn-Teller Distortion in a Pyrochlore System"Physical Review Letters. 85. 4960-4963 (2000)

[文献書誌] M.Oshikawa,K.Ueda,H.Aoki,A.,Ochiai and M.Koghi: "Field-Induced Gap Formation in Yb_4As_3"Journal of the Physical Society of Japan. 68. 3181-3184 (1999)

[文献書誌] H.Aoki,A.Ochiai,M.Oshikawa and K.Ueda: "Magnetic Anisotropy in Yb_4As_3 with One-dimensional Yb^<3+> Chains"Physica B. 281&282. 465-467 (2000)

[文献書誌] T.Akimoto,Y.Moritomo,A.Nakamura and N.Furukawa: "Observation of Anomalous Single-Magnon Scattering in Half-Metallic Ferromagnets by Chemical Pressure Control"Physical Review Letters. 85. 3914-3917 (2000)

[文献書誌] Y.Motome and N.Furukawa: "Critical Temperature of Ferromagnetic Transition in Three-Dimensional Double-Exchange Models"Journal of the Physical Society of Japan. 69. 3785-3788 (2000)

[文献書誌] N.Furukawa: "Unconventional One-Magnon Scattering Resistivity in Half-Metals"Journal of the Physical Society of Japan. 69. 1954-1957 (2000)

[文献書誌] T.Moriya and K.Ueda: "Spin Fluctuations and High-Temperature Superconducticity"Advances in Physics. 49. 555-606 (2000)

[文献書誌] H.Kontani,K.Kanki and K.Ueda: "Anomalous Behaviors of the Transport Phenomena in High-T_c Superconductors"Physica B. 281&282. 808-809 (2000)

[文献書誌] M.Sigrist et al.: "The Chiral p-Wave State in Sr_2RuO_4"Journal of the Physical Society of Japan : Supplement B. 69. 127-132 (2000)

[文献書誌] T.Morinari and M.Sigrist: "The Influence of Chiral Surface States on the London Penetration Depth in Sr_2RuO_4"Journal of the Physical Society of Japan. 69. 2411-2414 (2000)

[文献書誌] C.Honerkamp,K.Wakabayashi and M.Sigrist: "Instabilities at [110]-Surfaces of d_<x^2-y^2>-Wave Superconductors"Europhysics Letters. 50. 368-375 (2000)

[文献書誌] P.W.Brouwer,C.Mudry and A.Furusaki: "Nonuniversality in Quantum Wires with Off-Diagonal Disorder : A Geometric Point of View"Nuclear Physics B. 565. 653-663 (2000)

[文献書誌] P.W.Brouwer,C.Mudry and A.Furusaki: "Density of States in Coupled Chains with Off-Diagonal Disorder"Physical Review Letters. 84. 2913-2916 (2000)

[文献書誌] Y.Maeno,T.M.Rice and M.Sigrist: "The Intriguing Superconductivity of Strontium Ruthenate"Physics Today. 54,1. 42-47 (2001)

[文献書誌] S.Wessel,B.Normand,M.Sigrist and S.Haas: "Order by Disorder from Non-magnetic Impurities in a Two-dimensional Quantum Spin Liquid"Physical Review Letters. 86. 1086-1089 (2001)

[文献書誌] C.Honerkamp,M.Salmhofer,N.Furukawa and T.M.Rice: "Breakdown of the Landau-Fermi Liquid in Two Dimensions due to Umklapp Scattering"Physical Review B. 63. 035109-1,03510* (2001)

2000 年度実績報告書