Vibrational Coupling Modifies Spectral Diffusion in Core-Shell Colloidal Quantum Dots

TL;DR

This study uses two-dimensional spectroscopy to reveal how vibrational coupling with phonon modes influences spectral diffusion in core-shell quantum dots, showing deviations from expected dephasing behaviors.

Contribution

It demonstrates that LO-phonon mode coupling significantly alters exciton lineshapes and spectral diffusion in colloidal quantum dots, providing new insights into their ultrafast dynamics.

Findings

Observation of phonon sidebands in spectra

Deviations from exponential dephasing models

Vibrational coupling modifies spectral diffusion

Abstract

We perform two-dimensional coherent spectroscopy on CdSe/CdZnS core/shell colloidal quantum dots at cryogenic temperatures. In the two-dimensonal spectra, sidebands due to electronic coupling with CdSe lattice LO-phonon modes are observed that have evolutions deviating from the exponential dephasing expected from Markovian spectral diffusion. Comparison to simulations provides further evidence that the LO-phonon mode coupling itself significantly modifies the exciton lineshapes and results in the underlying spectral diffusion on ultrafast timescales.