| Project/Area Number |
17540305
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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 |
Condensed matter physics I
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
ISHIOKA Kunie National Institute for Materials Science, Advanced Nano-characterization center, Senior Researcher, ナノ計測センター, 主幹研究員 (30343883)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | coherent phonons / semiconductors / ultra fast dynamics / photo excitation / electron-phonon interaction / 固体物理学 / 強光子場 |
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| Research Abstract |
The present study has conducted experimental investigation on quantum interference of coherent optical phonons in semiconductors and semimetals under high-density photo excitation. The author and the coworkers had shown in the previous studies a striking amplitude collapse-revival of coherent symmetric phonons of semimetal Bi. In the present study, the author have performed a detailed and systematic pump-probe experiments on the symmetric and asymmetric phonon modes of Bi, as well as on phonon modes in other semiconductors and semimetals. The obtained experimental results lead to conclude that
(1)the generation of coherent phonons is not solely dominated by "Displacive Excitation", as it was considered for more than a decade, but is substantially contributed by stimulated Raman process. The amplitude collapse-revival is attributed to dynamic quantum interference between phononic and electronic states (Fano effect).
(2)the sub-linear power dependence of the phonon amplitude of CdTe is explained, from comparison with GaAs and Ge, to be due to the saturation of transient electric field screening at the surface.
(3)sub-10 fs laser pulses excites and probes the 40 THz coherent optical phonon in single crystal diamond. The coherent phonons are driven by electric field via resonant stimulated Raman process, without creating photo excited carriers.
These results demonstrate that a simple pump-probe reflectivity experiments provide a powerful tool to investigate the ultra fast dynamics of high-frequency phonons in solid materials in semiconductors and insulators, as well as their interaction with photo-excited carriers.
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