2002 Fiscal Year Annual Research Report

電子スピン共鳴によるスピンギャップ直接観測の理論的研究

Research Project

Project/Area Number	13640371
Research Institution	Tohoku University
Principal Investigator	坂井徹東北大学, 大学院・理学研究科, 助教授 (60235116)
Keywords	スピンギャップ / 低次元系 / 量子スピン系 / 強相関電子系
Research Abstract	反共磁性的なスピン間の交換相互作用を持ちながら、強い量子力学的効果のために極低温でも長距離秩序を示さない、低次元量子スピン系のスピンギャップを、電子スピン共鳴により直接観測できる可能性について理論的な研究を行った。本来このスピンギャップはスピン量子数が異なる状態間の遷移となるため、スピンの保存則から電子スピン共鳴では観測されないと考えられていたが、ここ数年いくつかの低次元スピン系でこの禁制遷移が観測され、そのメカニズム解明が注目されている。これまでの本研究により、このスピン保存則を破る遷移の起源として(1)磁性イオンのg-テンソルが交代するために生じる交代磁場、(2)結晶構造の非対称性からくるジャロシンスキー・守谷相互作用、(3)交換相互作用の異方性を想定し、ここの物質でこのうちのいずれが重要であるかを推定するための遷移の「選択則」を導いた。この選択則に照らしてこれまでの実験結果を解析し、いくつかの物質について判明したことを以下に記す。 1.CuGeO_3(スピンパイエルス系):選択則による実験結果の解析によると(1)が有力だが、強度の磁場依存性から(2)の可能性もある。 2.NENP(ハルデン系):選択則・磁場の強度依存性ともに(1)が重要であることが判明。 3.SrCu_2(BO_3)_2(2次元直行ダイマー系):結晶構造や中性子散乱の分散解析によると(2)が有力だが、選択則から(1)の可能性もある。上記の結果を2002年6月に仙台で開催されたInternational Workshop on application of submilimeter wave electron spin resonance for novel magnetic systemsにおいて招待講演を行い、他の研究者と討論した。

Research Products

(18 results)

All Other

All Publications (18 results)

[Publications] T.Sakai: "Electron spin resonance absorption from the ground state of gapped spin system"Physica Status Solidi(a). 189巻. 1063-1068 (2002)
[Publications] T.Sakai, Y.Takahashi: "Numerical Study on Pseudogap Phenomena in High-Tc Cuprates"Journal of Physics and Chemistry of Solid. 63巻. 1385-1388 (2002)
[Publications] N.Okazaki, K.Okamoto, T.Sakai: "Magnetization plateau in the S=1 spin ladder with competing interactions"Journal of Physics and Chemistry of Solid. 63巻. 1455-1458 (2002)
[Publications] K.Okamoto, N.Okazaki, T.Sakai: "Mechanism for non-trivial magnetization plateaux of an S=1 frustrated spin ladder"Journal of Physical Society of Japan supplement A. 71巻. 196-198 (2002)
[Publications] T.Sakai: "Charge Stripes Based on Higher-Order Interactions in Cuprate Superconductors"Physica C. 378巻-381巻. 208-211 (2002)
[Publications] S.Yamamoto, T.Sakai, A.Koga: "Re-Entrant Quantum Phase Transitions in Antiferromagnetic Spin-1 Ladders"Journal of Physical Society of Japan. 71巻. 1250-1253 (2002)
[Publications] S.Yamamoto, T.Sakai, A.Koga: "Quantum Phase Competition in Antiferromagnetic Spin-1 Ladders"Progress on Theoretical Physics Supplement. 145巻. 176-181 (2002)
[Publications] O.Cepa, T.Sakai, T.Ziman: "Dynamics, Selection Rules and Dzyaloshinski-Moriya Interaction in Strongly Frustrated Magnets"Progress on Theoretical Physics Supplement. 145巻. 43-51 (2002)
[Publications] T.Sakai, M.Takahashi: "Spin flop in 1D quantum antiferromagnets"Progress on Theoretical Physics Supplement. 145巻. 125-129 (2002)
[Publications] T.Sakai, K.Okamoto: "Quantum magnetization plateaux of an anisotropic ferrimagnetic chain"Physical Review B. 65巻. 214403-1-214403-6 (2002)
[Publications] T.Sakai, N.Okazaki, T.Ohnishi, S.Takemura: "ESR selection rules for direct transition of spin gap"EPR in the 21th Century : Basic and Applications to Material, Life and Earth Sciences edited by A Kawamori et al.(Elsevier). 54-58 (2002)
[Publications] T.Sakai, K.Okamoto, N.Okazaki: "Field-induced transitions and spin gaps in low-dimensional quantum antiferromagnets"Quantum Properties of Low-Dimensional Antiferromagnets, edited by Y Aiiro and J-P Boucher(Kyushu University Press). 62-69 (2002)
[Publications] T.Sakai, N.Okazaki, K.Okamoto, K.Kindo, Y.Narumi, Y.Hosokoshi et al.: "Magnetization plateaus in S=1 spin ladder"Physica Status Solidi. 236巻. 429-432 (2003)
[Publications] T.Sakai: "Direct Observation of Spin Gaps in Electron Spin Resonance"Journal of Physical Society of Japan supplement A. 72巻(掲載予定). (2003)
[Publications] T.Sakai: "Charge stripes and four-spin exchange interaction in high-Tc cuprates"Acta Physica Polonica B. (掲載予定). (2003)
[Publications] K.Okamoto, T.Sakai: "Spin-Peierls mechanism for the non-trivial magnetization plateaux in two-leg"Physica B. (掲載予定). (2003)
[Publications] T.Sakai, N.Okazaki, K.Okamoto, K.Kindo, Y.Narumi, Y.Hosokoshi et al.: "Magnetization plateaux in S=1 Organic Spin Ladder BIP-TENO"Physica B. (掲載予定). (2003)
[Publications] T.Sakai: "Investigation of Charge Stripe Formation in an Extended t-J Model"Journal of Physics A. (掲載予定). (2003)

2002 Fiscal Year Annual Research Report

電子スピン共鳴によるスピンギャップ直接観測の理論的研究

Principal Investigator

坂井 徹 東北大学, 大学院・理学研究科, 助教授 (60235116)

Research Products

[Publications] T.Sakai: "Electron spin resonance absorption from the ground state of gapped spin system"Physica Status Solidi(a). 189巻. 1063-1068 (2002)

[Publications] T.Sakai, Y.Takahashi: "Numerical Study on Pseudogap Phenomena in High-Tc Cuprates"Journal of Physics and Chemistry of Solid. 63巻. 1385-1388 (2002)

[Publications] N.Okazaki, K.Okamoto, T.Sakai: "Magnetization plateau in the S=1 spin ladder with competing interactions"Journal of Physics and Chemistry of Solid. 63巻. 1455-1458 (2002)

[Publications] K.Okamoto, N.Okazaki, T.Sakai: "Mechanism for non-trivial magnetization plateaux of an S=1 frustrated spin ladder"Journal of Physical Society of Japan supplement A. 71巻. 196-198 (2002)

[Publications] T.Sakai: "Charge Stripes Based on Higher-Order Interactions in Cuprate Superconductors"Physica C. 378巻-381巻. 208-211 (2002)

[Publications] S.Yamamoto, T.Sakai, A.Koga: "Re-Entrant Quantum Phase Transitions in Antiferromagnetic Spin-1 Ladders"Journal of Physical Society of Japan. 71巻. 1250-1253 (2002)

[Publications] S.Yamamoto, T.Sakai, A.Koga: "Quantum Phase Competition in Antiferromagnetic Spin-1 Ladders"Progress on Theoretical Physics Supplement. 145巻. 176-181 (2002)

[Publications] O.Cepa, T.Sakai, T.Ziman: "Dynamics, Selection Rules and Dzyaloshinski-Moriya Interaction in Strongly Frustrated Magnets"Progress on Theoretical Physics Supplement. 145巻. 43-51 (2002)

[Publications] T.Sakai, M.Takahashi: "Spin flop in 1D quantum antiferromagnets"Progress on Theoretical Physics Supplement. 145巻. 125-129 (2002)

[Publications] T.Sakai, K.Okamoto: "Quantum magnetization plateaux of an anisotropic ferrimagnetic chain"Physical Review B. 65巻. 214403-1-214403-6 (2002)

[Publications] T.Sakai, N.Okazaki, T.Ohnishi, S.Takemura: "ESR selection rules for direct transition of spin gap"EPR in the 21th Century : Basic and Applications to Material, Life and Earth Sciences edited by A Kawamori et al.(Elsevier). 54-58 (2002)

[Publications] T.Sakai, K.Okamoto, N.Okazaki: "Field-induced transitions and spin gaps in low-dimensional quantum antiferromagnets"Quantum Properties of Low-Dimensional Antiferromagnets, edited by Y Aiiro and J-P Boucher(Kyushu University Press). 62-69 (2002)

[Publications] T.Sakai, N.Okazaki, K.Okamoto, K.Kindo, Y.Narumi, Y.Hosokoshi et al.: "Magnetization plateaus in S=1 spin ladder"Physica Status Solidi. 236巻. 429-432 (2003)

[Publications] T.Sakai: "Direct Observation of Spin Gaps in Electron Spin Resonance"Journal of Physical Society of Japan supplement A. 72巻(掲載予定). (2003)

[Publications] T.Sakai: "Charge stripes and four-spin exchange interaction in high-Tc cuprates"Acta Physica Polonica B. (掲載予定). (2003)

[Publications] K.Okamoto, T.Sakai: "Spin-Peierls mechanism for the non-trivial magnetization plateaux in two-leg"Physica B. (掲載予定). (2003)

[Publications] T.Sakai, N.Okazaki, K.Okamoto, K.Kindo, Y.Narumi, Y.Hosokoshi et al.: "Magnetization plateaux in S=1 Organic Spin Ladder BIP-TENO"Physica B. (掲載予定). (2003)

[Publications] T.Sakai: "Investigation of Charge Stripe Formation in an Extended t-J Model"Journal of Physics A. (掲載予定). (2003)

坂井徹東北大学, 大学院・理学研究科, 助教授 (60235116)