1996 Fiscal Year Final Research Report Summary
Study on Bose-Einstein Condensation of Biexciton Systems by Phase-conjugation Spectroscopy
| Project/Area Number |
05402008
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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Ⅰ(光物性・半導体・誘電体)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NAGASAWA Nobukata The University of Tokyo, School of Science, Professor, 大学院・理学系研究科, 教授 (50004437)
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| Co-Investigator(Kenkyū-buntansha) |
HASUO Masahiro The University of Tokyo, School of Science, Research Assistant, 大学院・理学系研究科, 助手 (40218433)
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| Project Period (FY) |
1993 – 1996
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| Keywords | Semiconductor / Exciton / Biexciton / Bose condensation / Phase-conjugation / Nonlinear optics / CuCl / Cu_2O |
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| Research Abstract |
An excitonic particle such as an exciton or a biexciton in a semiconductor crystal has a boson-like nature. It has been expected that the transition to Bose condensed phase of the excitonic particles occurs under a high density photo-excitation by laser light. The porpose of this research is to examined the expectation experimentally by means of a nonlinear optical aim of phase-conjugation spectroscopy.
In the biexciton system in CuCl, following results were obtained :
1. distributions of biexcitons were reproduced by Bose distribution functions in an incoherent excitation regime,
2. under the condition a remarkable enhancement of the phase-conjugate (PC) signal intensity was observed. The enhancement was observed correlatively when the biexciton density was beyond the critical density for the Bose-Einstein condensation, and
3.100% enhancement of the PC signal intensity was realized at the maximam under the injection of incoherent biexcitons.
In the exciton system in Cu_2O,following results were obtained :
1. distributions of excitons were well reproduced by Bose distribution functions,
2. a new method to generate very cold and spatially uniformed ortho-excitons using a two-photon resonant excitation was developed,
3. the distribution of ortho-excitons under the two-photon resonant excitation is reproduced by a Bose distribution function with a low temperature. The result suggested that the condition of the ortho-excitons was very close to the phase boundary for the Bose-Einstein condensation,
4. it was confirmed that the phase-conjugation spectroscopy were applicable to the study of the Bose-Einstein condensation in ortho-exciton system from the measurement of the polarization characteristics of the two-photon transition.
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