Coherent control of charge and lattice dynamics in a photoinduced neutral-to-ionic transition of a charge-transfer compound.

Coherent control of a charge-lattice coupled oscillation associated with the neutral (N)-ionic (I) transition was successfully demonstrated for a charge-transfer (CT) compound, tetrathiafulvalene-p-chloranil, with use of double femtosecond laser pulses. By changing the interval of the two laser pulses, amplitude of the oscillation in the reflectivity for the intramolecular transition band sensitive to the degree of CT was periodically changed. With increase of the pump intensity, the oscillation amplitude was dramatically enhanced. Such an enhancement is discussed in terms of the cooperative nature of the N-I transition.