Local response to light excitation in the charge-ordered phase of (EDO-TTF)2Sb F6

The family of materials (EDO-TTF)2XF6 represents quasi-one-dimensional quarter filled systems exhibiting insulator-to-metal (I-M) phase transition at thermal equilibrium. (EDO-TTF)2PF6 is known to undergo a photoinduced I-M conversion with cooperative response to light excitation. Here we use femtosecond pump-probe experiments to study the photoresponse of (EDO-TTF)2SbF6 made of a larger counteranion SbF6 compared to the well studied (EDO-TTF)2PF6. In the early stage of the photoinduced process, we reveal a multicomponent coherent oscillating feature. The evolution of this feature with excitation density and temperature points to the local nature of the photoswitching in (EDO-TTF)2SbF6. At longer time scale, we did not detect the features associated with the transformation to the M phase, albeit observed in the PF6 derivative. We propose a scenario whereby the bigger size of the counteranion in (EDO-TTF)2SbF6 hinders the establishment of this transformation at macroscopic scale.