  Addressing the role of quantum coherence in the interplay between the
different matter constituents (electrons, phonons and spin) is a critical step
towards understanding transition metal oxides and design complex materials with
new functionalities. Here we use coherent vibrational control of onsite d-d
electronic transitions in a model edge-sharing insulating transition metal
oxide (CuGeO3) to single-out the effects of vibrational coherence in
electron-phonon coupling. By comparing time domain experiments based on high
and low frequency ultrashort pumps with a fully quantum description of phonon
assisted absorption, we could distinguish the processes associated to
incoherent thermal lattice fluctuations from those driven by the coherent
motion of the atoms. In particular, while thermal fluctuation of the phonon
bath uniformly increases the electronic absorption, the resonant excitation of
phonon modes results also in light-induced transparency which is coherently
controlled by the vibrational motion.
