Coherent dynamics of the charge density wave gap in tritellurides

The dynamics of the transient electronic structure in the charge density wave (CDW) system RTe3 (R = rare-earth element) is studied using time- and angleresolved photoemission spectroscopy (trARPES). Employing a three-pulse pumpprobe scheme we investigate the effect of the amplitude mode oscillations on the electronic band structure and on the CDW energy gap. We observe coherent oscillations in both lower and upper CDW band with opposite phases, which two dominating frequencies modulating the CDW order parameter. This demonstrates the existence of more than one collective amplitude mode, in contrast to a simple Peierls model. Coherent control experiments of the two amplitude modes, which are strongly coupled in equilibrium, demonstrate independent control of the modes suggesting a transient decoupling of both mode