Electron dynamics in two-dimensions: a hunt for the ground-state polarons

The semi-classical Holstein model is used to account for experimental observations of electron dynamics in two-dimensional systems and assign transient spectral features formerly attributed to formation of small polarons. Our results show that the intraband relaxation of initial Bloch states is not directly followed by formation of the ground-state small polarons, but proceeds through transient long-lived intermediate states with energies near the bottom of the Bloch band. The calculations are in agreement with pump-probe experiments on ultrafast electron dynamics at metal-organics interfaces and suggest a novel interpretation of the dispersionless structures always observed near the bottom of the Bloch band.