Ultrafast optical switching from an ionic to a neutral state in tetrathiafulvalene-p-chloranil (TTF-CA) observed in femtosecond reflection spectroscopy

Ultrafast optical switching from an ionic (I) to a neutral (N) state in TTF-CA was observed in femtosecond reflection spectroscopy. Charge transfer excitation in the I phase produces N donor (D-0) acceptor (A(0)) strings within 2 ps. These initial N states decay, with a lifetime of 300 ps at 4 K, but rather multiply leading to macroscopic I-N conversion within 20 ps at 77 K just below the N-I transition temperature T-NI. Near T-NI, we also found the evidence for the coherent motion of the macroscopic N-I domain boundary with a period of 85 ps.