Dephasing processes that give rise to homogeneous broadening play a role in transport processes that depends on their origin. For example, electron-phonon coupling is usually detrimental for transport, but the role of intervalley splittings (analogous to the Jahn-Teller effect in molecules) and fine-structure arising from the spin-orbit interaction is not yet clear. Lead sulfide quantum dots have been variously reported to show electronic dephasing of the bandgap transition on timescales from 5 fs to 100 fs. Explaining the reported timescales has been problematic. In colloidal PbS quantum dots, the initial dynamics are obscured by non-resonant cross-phase modulation signals from the solvent. This unwanted signal from the solvent becomes larger when short 15 fs pulses that cover the bandgap transition are used to record the PbS 2D spectra. Experiments and simulations of the 2D spectra from the quantum dot solution (PbS plus solvent 2D spectra) and the neat solvent (solvent 2D spectra) are used to separate these two signals in order to isolate the dynamics of the quantum dot 2D spectra. In the colloidal solution, the solvent 2D spectra are modified by PbS quantum dot absorption of the excitation fields and signal, and cannot be simply subtracted, but can be accurately simulated using a 3D FT algorithm. The dynamics in the PbS 2D spectra will be discussed.

Fast electronic dynamics in 2D spectra of PbS quantum dots

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.