| Project/Area Number |
12640338
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | CHIBA UNIVERSITY |
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Principal Investigator |
YUDSON Vladimir Chiba University, Center for Frontier Science, Professor, 先進科学教育センター, 教授 (00322032)
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| Co-Investigator(Kenkyū-buntansha) |
INOUE Junichi Chiba University, Center for Frontier Science, Assistant, 先進科学教育センター, 助手 (90323427)
OHTAKA Kazuo Chiba University, Center for Frontier Science, Professor, 先進科学教育センター, 教授 (40010946)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2001: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | random media / mesoscopics / nanostructures / weak localization / interaction / nonlinear response / メソスコピック系 / 永久電流 / 量子井戸 / 励起子 |
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| Research Abstract |
Motivated by experimental investigations of persistent electric currents in mesoscopic normal metal rings threaded by a magnetic flux, we have studied a contribution to the time-independent current that arises due to electron interaction with an external ac electromagnetic field. Theory of the nonlinear response of mesoscopic electron systems to a time-dependent external field has been developed with the use of the Keldysh formalism. It has been shown that the nonlinear response of closed mesoscopic systems differs remarkably from the response of open systems. The developed theory is applied for the analysis of mesoscopic variations of the time-independent current in mesoscopic rings in the presence of an ac pumping. The current-current correlation function is shown to be very sensitive to the spectral width of the external field and to possess different symmetries with respect to the magnetic flux inversion. These observations are favorable for a hypothesis about a considerable noise-
… More
induced component of observable time-independent currents in metal rings.
We have considered also a classical analog of quantum mesoscopic phenomena. Namely, diffusion in narrow channels with varying boundaries has been studied. Boundary variations may result in a considerable change of the particle transport and, in particular, in a nonlinearity of the response to an external field. A difference between nonlinear responses of open and closed channels has been demonstrated. This is similar to the difference of responses from canonical and grand-canonical quantum mesoscopic systems.
Finally, interaction and disorder effects have been studied for a system of indirect excitons in double quantum wells (DQW) excited by a laser pump. It has been shown that in a low excitation regime the dipole-dipole repulsion of indirect excitons modifies the balance between the rate of exciton collection by a puddle (droplet) of a dense "liquid" state and the recombination rate of the puddle. This leads to a novel limitation on the puddle size and on the formation of an inhomogeneous ("droplet-vapor") state. On the contrary, the presense of disorder may promote the formation of droplets. These findings are applied for a discussion of recent experiments in the field. Less
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