New Developments in the Theory of Non-Magnetic Ground State and Magnetic-Field-Induced Spin Gap in Low Dimensional Spin Systems
Grant-in-Aid for Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||Tokyo Institute of Technology|
OKAMOTO Kiyomi Tokyo Institute of Technology, Graduate School of Science and Engineering, Assistant Professor, 大学院・理工学研究科, 助手 (40152342)
|Project Period (FY)
2002 – 2005
Completed(Fiscal Year 2005)
|Budget Amount *help
¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 2005 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 2004 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 2003 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 2002 : ¥1,700,000 (Direct Cost : ¥1,700,000)
|Keywords||low-dimensional magnets / spin chain / quantum phase transition / spin gap / magnetization plateau / magnetization curve / 磁場誘起スピンギャップ / 非磁性性基底状態 / 量子スピン / フラストレーション / 磁性体 / 磁気相図 / 非磁性基底状態 / スピン液体 / 低次元系 / レベルスペクトロスコピー / BIP-TENO / アズライト|
By use of analytical and numerical methods, we have investigated the ground states with zero or finite magnetic fields for various one-dimensional and quasi-one-dimensional spin systems. Especially, we have focused on the spin-gap states in zero or finite magnetic fields.
1. We have proposed several mechanisms for the magnetic-filed-induced spin gap at 1/4 of the saturation magnetization of a ladder type organic spin system BIP-TENO. We have succeeded to explain the behavior of the observed magnetization curve.
2. We have studied the distorted diamond type spin chain, by use of analytical and numerical methods, especially focusing on the ground states in zero and finite magnetic field. In this system, there appears various phases depending upon the quantum parameters. In particular, it was found the change in the mechanism for the magnetization plateau at 1/3 of the saturation magnetization. The magnetic properties of azurite are well described by this model.
3. We have obtained the definitive conclusion on the phase diagram of the spin ladder with the bond alternation.
4. We have found the inversion phenomenon between the anisotropies of the Hamiltonian and the wave function for the spin systems with three keywords : trimer nature, frustration and the XXZ anisotropy of the spin-spin interactions. Namely, in some regions of the quantum parameters, the Neel ground state is realized in spite of the fact that the interactions is XY-like. And also, the spin-fluid ground state is realized when the interaction is Ising-like.
5. We have clarified the condition for the appearance of the spin orderng which is incommensurate to the lattice for the material F5PNN.
Research Products (100results)