Ultrafast nonlinear optical response and high density excitation effects of the stacking fault exciton in BiI3 |
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Authors: | T Karasawa M Ichida I Akai T Komatsu |
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Institution: | (1) Department of Physics, Osaka City University, Sumiyoshi-ku, 558 Osaka, Japan |
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Abstract: | On the exciton states localized at a two-dimensional stacking fault interface in a layered crystal BiI3, some nonlinear optical phenomena clearly appear reflecting large transition probability. The optical Stark shift and other high density exciton effect on the energy-shift and the spectral broadening are observed with clear separation under intense laser pumping by time-resolved measurements. The optical Stark shift is analyzed based on the dressed exciton model. The ultrafast optical response faster than 3 ps for the pump-laser field is confirmed on the Stark shift. Degenerate four-wave-mixing signals show fairly long dephasing time of 40 ps in this system. The dephasing probability depends linearly on the pump-laser intensity in the same manner as that of the spectral line-broadening reflecting the relaxation process. The dephasing mechanisms are understood by the exciton scattering at high density in parallel with the spectral changes. The blue-shift due to the high density excitons are discussed on the basis of exciton-exciton interaction in connection with a phase-space filling theory in two-dimensional systems. |
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Keywords: | 71 70 Ej 71 35 +z 73 40 Lq |
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