| Project/Area Number |
10203205
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas (B)
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| Allocation Type | Single-year Grants |
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| Research Institution | The University of Tokyo |
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Principal Investigator |
ISHIMOTO Hidehiko University of Tokyo, ISSP, Prof., 物性研究所, 教授 (60044773)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAGUCHI Akira University of Tokyo, ISSP, Res. Asso., 物性研究所, 助手 (10302639)
YOSHITOMO Karaki University of Tokyo, ISSP, Res. Asso., 物性研究所, 助手 (30186027)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥21,600,000 (Direct Cost: ¥21,600,000)
Fiscal Year 2000: ¥4,400,000 (Direct Cost: ¥4,400,000)
Fiscal Year 1999: ¥7,700,000 (Direct Cost: ¥7,700,000)
Fiscal Year 1998: ¥9,500,000 (Direct Cost: ¥9,500,000)
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| Keywords | spin liquid / frustration / multiple spin exchange / triangular lattice / antiferromagnet / quantum solid / quantum spin / low dimension / 子流体 |
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| Research Abstract |
A low density solid ^3He film adsorbed on graphite is proved to be one of the most ideal two dimensional S=1/2 antiferromagnets on a triangular lattice. Due to the hard-core potential between ^3He atoms, the higher order multiple spin exchange (MSE) processes as well as two-particle exchange play important. The exchange of even number of pairticles is antiferromagnetic (AFM), whereas that of odd ones is ferromagnetic (FM). The competition between them, in addition to the geometrical frustration, makes this system strongly frustrated. A recent calculation of the exact diagonalization for a finite system predicts a possible "quantum spin liquid" ground state with an excitation gap. NMR studies of sub-monolayer ^3He adsorbed on two and three layers of HD preplated graphite have been made down to 100μK which is more than one order of magnitude smaller than the exchange energy (J). In the highly frustrated antiferromagnetic solid region, the magnetization obeys a Curie-Weiss law even at the temperatures around J and then increases gradually down to 100 mK. Nevertheless it does not show any anomalous behavior corresponding to the existence of spin gap. The normalized magnetization vs. the reduced temperature (T/J) is independent of the density just after solidification. This fact is consistent with the result observed in the high temperature region that the main multiple spin exchanges have similar density dependence.
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