Snapshots of cooperative atomic motions in the optical suppression of charge density waves

The development of tabletop femtosecond electron diffraction sources has provided an alternative way of observing atomic motions in crystalline materials. This technique has now been applied to the charge-density-wave material 1T-TaS2, in which modulation of the electron density is accompanied by a periodic lattice distortion. Previous time-resolved studies have revealed the dynamics of the electronic charge density wave, but until now the dynamics of the lattice system has been only indirectly inferred. In this new experiment, atomic motions were observed in response to a 140 femtosecond optical pulse. Periodic lattice distortion was seen to collapse on an exceptionally fast timescale (about 250 fs), indicative of an electronically driven process involving a high degree of cooperativity. The surprisingly high degree of cooperation in the observed structural dynamics between the electronic and lattice system illustrates the potential for the technique in studies of strongly correlated systems.