| Project/Area Number |
10203201
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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 | Tohoku University |
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Principal Investigator |
SAWADA Anju Tohoku University, Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (90115577)
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| Co-Investigator(Kenkyū-buntansha) |
OHNO Yuzo Tohoku University, Research Institute of Electrical Communication, Research Associate, 電気通信研究所, 助手 (00282012)
EZAWA Zyun francis Tohoku University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (90133925)
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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 |
¥8,800,000 (Direct Cost: ¥8,800,000)
Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1999: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1998: ¥3,100,000 (Direct Cost: ¥3,100,000)
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| Keywords | Quantm Hall Effect / Composite Boson / Activation Energy / Interlayer Coherence / Bose Condensation / Skyrmion / Pseudospin / Spin / ホールプラトー / 層間コヒーレント / ガリウム砒素 / ホールプラントー |
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| Research Abstract |
The activation energy was measured in the bilayer quantum Hall (QH) state at filling factor ν = 2 and 1, by changing the total electron density and the density ratio in the two quantutn wells. The ν = 1 state is found stable over all measured range of the density difference. The ν = 2 state, on the other hand, shows a phase transition between these two types of the states as the electron density is changed. The ν = 1 state is a "coherent" state stabilarized by the strong interlayer Coulomb interaction. The ν = 2 state shows a phase transition from the compound state to the "coherent" state as the interlayer Coulomb interaction becomes dominant. The appearance of such ν = 2 "coherent" state is a consequence of the spin degree of freedom in the bilayer QH state.
We have measured the activation energy of the ν = 2 QH state at the balanced point (n_f = n_b) and the ν = 1 QH state at the monolayer point (n_f ≠ 0, n_b = 0) by tilting the samples. Skyrmion excitations were measured and compared for the flrst time in the QH state at the Landau-level filling factor ν = 2 and in the monolayer QH state at ν = 1. The observed number of flipped spins, N_<spin>, is 14 in the bilayer sample with a large tunnelling gap, and N_<spin> = 7 in the bilayer sample with a small tunnelling gap, while it is N_<spin> = 7 in the monolayer sample. The difference is interpreted to be due to the interlayer exchange interaction.
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