Photo-induced insulator-metal transition in an organic conductor α-(BEDT-TTF)2I3

Photo-switching between a charge-ordered insulating (CO) state and a metallic (M) state has been successfully realized in an organic conductor alpha-(BEDT-TTF)(2)I-3 at low temperatures. The large photocurrent induced by the pulsed laser excitation with a photon energy of 2.6 eV had two components. The fast-decaying component had a life time of 120ns. The subsequent one rose slowly (after about 0.7 mus) and remained as long as an electric field above 470 V/cm was applied. The dependences of these two components on laser power, applied voltage, and the onset of pulsed voltage were examined. It has been clearly demonstrated that the second component has prominent thresholds for both laser power and voltage. For each component, the resistivity decreased by about seven orders of magnitude from about 4 MOmega(.)cm to less than 0.4 Omega(.)cm at 4 K.