Hydrostatic pressure effect on photoinduced insulator-to-metal transition in the layered organic salt α- (BEDT-TTF)2 I3

The effect of high pressure on the photoinduced insulator-to-metal transition in charge-ordered [bis(ethylenedithio)]tetrathiafulvalene (BEDT-TTF) salt α- (BEDT-TTF)2 I3 was investigated using femtosecond spectroscopy under hydrostatic pressure. By applying pressure (P), the lifetime of the initially produced microscopic metallic domain becomes shorter, reflecting that condensation to the semimacroscopic metallic state is disturbed for P<0.5 GPa. However, condensation is promoted for P=0.5-1 GPa, thereby enhancing the nonlinearity of the photoinduced insulator-to-metal transition. Such nonmonotonous pressure dependence suggests competition between the increase of electronic bandwidth and photoinduced anisotropic lattice strain under pressure.