Phonon induced pure dephasing process of excitonic state in colloidal semiconductor quantum dots

• Pure dephasing time of spherical semiconductor quantum dot is calculated.
• Optical phonon mode dominates the pure dephasing process.
• Pure dephasing time nonlinearly increases with decreasing phonon coupling.
• Pure dephasing time of large quantum dots is more sensitive on temperature.

We present a theoretical study on the pure dephasing process of colloidal semiconductor quantum dots induced by lattice vibrations using continuum model calculations. By solving the time dependent Liouville-von Neumann equation, we present the ultrafast Rabi oscillations between excitonic state and virtual state via exciton-phonon interaction and obtain the pure dephasing time from the fast decayed envelope of the Rabi oscillations. The interaction between exciton and longitudinal optical phonon vibration is found to dominate the pure dephasing process and the dephasing time increases nonlinearly with the reduction of exciton-phonon coupling strength. We further find that the pure dephasing time of large quantum dots is more sensitive to temperature than small quantum dots.