In this study, we have investigated the ultrafast photoinduced dynamics of ${\left(\mathrm{EDO}\text{−}\mathrm{TTF}\right)}_2{\mathrm{SbF}}_6$ single crystals under hydrostatic pressure. Our results indicate the occurrence of the charge-ordering phase transition under hydrostatic pressure at room temperature around 2200 bar. This leads to the appearance of oscillatory components into the ultrafast transient photoresponse. This periodic signal is associated with the ultrafast generation of coherent phonons, a clear marker of the insulating charge-ordered phase while photoexcited with ultrashort pulses. The photoinduced dynamics display a strong anisotropic character and an additional slower dynamic involving thermoelastic effects. Furthermore, a peculiar photoresponse at very high pressure (5500 bar) suggests the occurrence of a second phase transition, leading to a possible new charge-ordered state which is absent in the thermally driven case. This finding is supported by the presence of a new coherent phonon mode whose frequency of $\approx 1.7$ THz does not match the ones observed in the two phases present at thermal equilibrium under ambient pressure.

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• Charge dynamics
• Optical phonons
• Phase transitions
• Photoinduced effect
• Femtosecond laser spectroscopy
• Pressure techniques
• Transient absorption spectroscopy
• Ultrafast femtosecond pump probe