2005 Fiscal Year Final Research Report Summary
Quantum mechanical response to time-dependent external field and related cooperative phenomena
| Project/Area Number |
16540308
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MIYASHITA Seiji The University of Tokyo, Physics, Professor, 大学院・理学系研究科, 教授 (10143372)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Keiji The University of Tokyo, Physics, Research Associate, 大学院・理学系研究科, 助手 (90312983)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Quantum dynamics / Landau-Zener Transition / Spin-crossover / Quantum phase transition / Metastable state |
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| Research Abstract |
We have studied on the following theme and published papers as listed in the separated sheet and also gave talks including several invited talks.
We studied characteristics of time evolution of quantum systems under time-dependent external fields from a view point of microscopic energy levels. We found that the energy structure of V15 is sensitively changes with the direction of the Dzyaloshinski-Moriya interaction. The effect of energy dissipation on the magnetization process was also studied by making use of quantum master equation. We also studied phase transition and cooperative phenomena due to quantum mechanical properties. We obtain the ground state phase diagram of XY-like Heisenberg antiferromagnets on the triangular lattice. There various phases appear as a function of anisotropy and the external magnetic field, which is attributed to the quantum fluctuation playing the role of thermal fluctuation at finite temperatures. We also studied the energy gap in the triangle spin-tube. We found systems where the magnetization does not fit with the lattice unit. We also study a new type of quantum fluctuation induced magnetic order in the quantum Blume-Capel model. The phase transition and the existence of metastable structures in the spin-crossover material were also studied. Slow relaxation processes in the strongly frustrated system were studied and found new type of slow relaxation, i.e. entropy-induced slow relaxations.
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