Abstract
We report on the generation of coherent optical phonons in $\mathrm{Cs}\mathrm{Pb}{\mathrm{Cl}}_{3}$ nanocrystals in CsCl by femtosecond laser-pulse illumination. Four phonon modes were identified in the measured oscillations of transient transmission with frequencies matching well those of the lowest confined optical-phonon modes in $\mathrm{Cs}\mathrm{Pb}{\mathrm{Cl}}_{3}$ nanocrystals. The temperature dependence of the phonon mode softening and oscillation damping was used to identify the phonon dephasing mechanisms. It was shown that the main contribution is due to the effect of cubic anharmonicity of the lattice. The possible role of the spatial confinement of phonons in the volume of nanocrystals and the effects of the nanocrystal size distribution in the oscillation damping are also discussed.
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