Control of Phonons in Semiconductor Nanocrystals via Femtosecond Pulse Chirp-Influenced Wavepacket Dynamics and Polarization

摘要

The realistic electronic structure of semiconductor nanocrystals is characterized by excitonic fine structure and atomistic symmetry breakings that are challenging to resolve experimentally. Exciton—phonon coupling is one of the most sensitive measures of the excitonic wave functions of the nanocrystals. Here, we exploit this sensitivity via chirped pulse and polarization resolved femtosecond pump/probe spectroscopy of colloidal CdSe nanocrystals. Pulse chirp measurements and simulations are used to explore the contributions of excited- and ground-state vibrational wavepackets to the observed coherent phonons in the pump/probe signals. Polarization resolved pump /probe spectroscopy is used to explore electronic and vibrational polarization anisotropics. We find no electronic polarization anisotropy, whereas vibrational anisotropy is preserved.