| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
In this project, we have studied a variety of interesting phenomena in strongly correlated electron systems, which are subject to geometrical frustration under the influence of spin and orbital degrees of freedom. We have also aimed at comprehensive understanding of the fundamental problem of condensed matter physics, i.e. "electron correlations and quantum fluctuations". In order to theoretically treat these systems with large quantum fluctuations, we need make use of sophisticated methods beyond mean-field theory. In general, it is difficult to deal with such problems including both strong electron correlations and geometrical frustration. We have used a powerful method, the so-called dynamical cluster approximation, which enables us to study frustrated electron systems systematically. Also, we have exploited the computer-aided strong-coupling cluster expansion when we approach the problem from the insulating side, while in the metallic region, we have used the variational Monte Carl
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o method, etc. We have systematically investigated the interesting phenomena originating from the interplay of spin, charge and orbital degrees of freedom. In particular, we have focused on quantum phase transitions and related critical phenomena. In this way, we have studied the dynamics of strongly correlated electron systems theoretically from the microscopic point of view. We have investigated the above problem with particular emphasis on the following six subjects.
1.hole-doing effect into frustrated Mott insulator.
2.frustration effects in spin-ice systems.
3.spontaneous dimensional-reduction due to frustration
4.competition between the Kondo effect and the RKKY interaction.
5.competition and interplay between spin and orbital degrees of freedom.
6.correlated electron systems on the Kagome and checker-board lattice.
The above results have been published (30 original papers) in several international journals. Also, we have reported the results (12 invited talks) in the international conferences and symposia. Although the research has been performed systematically, there still remains the quantitative comparison with experiments, which will be considered in the future work. Less
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