| Project/Area Number |
13130101
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | TOKYO INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
TANAKA Hidekazu Tokyo Institute of Technology, Research Center for Low temperature Physics, Professor, 極低温物性研究センター, 教授 (80188325)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Yutaka University of Tokyo, Institute for Solid State Physics, Professor, 物性研究所, 教授 (20127054)
KINDO Koichi University of Tokyo, Institute for Solid State Physics, Professor, 物性研究所, 教授 (20205058)
OHTA Hitoshi Kobe University, Molecular Photoscience Research Center, Professor, 分子フォトサイエンス研究センター, 教授 (70194173)
宮下 精二 東京大学, 大学院・理学研究科, 教授 (10143372)
利根川 孝 福井工業大学, 工学部, 教授 (80028167)
内野倉 國光 東京大学, 大学院・新領域創成科学研究科, 教授 (20015564)
本河 光博 東北大学, 金属材料研究所, 教授 (30028188)
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| Project Period (FY) |
2001 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥28,200,000 (Direct Cost: ¥28,200,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2004: ¥9,200,000 (Direct Cost: ¥9,200,000)
Fiscal Year 2003: ¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 2002: ¥6,400,000 (Direct Cost: ¥6,400,000)
Fiscal Year 2001: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Keywords | Magnetism / Experiments for Solid State Physics / Low Temperature Physics / Statistical Mechanics / High Magnetic Field / Quantum Spin Systems / Field-Induced Magnetic Phenomena / Low Dimensional Magnets / 強磁場物性 / 高圧物性 / スピンギャップ / 量子相転移 / 量子効果 / 新物質 / フラストレーション |
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| Research Abstract |
We have developed many quantum magnets, which have various crystal structures, and have investigated their magnetic properties in high magnetic fields. Followings are representative results. Coupled S=1/2 spin dimer systems undergo novel quantum phase transitions in high magnetic fields. These systems often have singlet ground states with excitation gaps. In high magnetic field, one of the triplets whose energy decreases with magnetic field plays an important role. The triplet can hop to neighboring site as a quasi-particle and interact due to the transverse and longitudinal components of the interdimer exchange interaction. The quasi-particle has characteristics of boson and is called magnon or triplon. Consequently, the system can be described as interaction boson system, where magnetic field corresponds to the chemical potential. We found that the magnetization plateaus in SrCu_2(BO_3)_2 and other systems. The magnetization plateau can occur when the hopping of magnons are strongly
… More
suppressed due to spin frustration or parity and the periodic arrangement of magnons (Wigner crystal) are stabilized due to the repulsive interaction. This is a typical quantum many-body effect By means of NMR in high magnetic fields on SrCu_2(B0_3)_2, we verify the realization of Wigner crystal of magnons. On the other hand, the field-induced antiferromagnetic (AF) ordering occurs when the hopping of magnons is dominant The ordering can be described as the Bose-Einstein condensation (BEC) of magnons. We have performed various measurements on the field-induced AF ordering in TlCuCl_3. Together with theoretical analysis, we verify that the field-induced AF ordering in TlCuCl_3 is the BEC of magnons. The present study demonstrated that there are cases where the quantum magnets exhibit the nature characteristic of ensemble of quantum particles. This provides a new concept of magnetism.
To encourage our research project, we organized three open symposiums inviting researchers from abroad and International Symposium on Quantum Spin Systems QSS04. We also supported three international meetings. Less
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