Photo-induced phase transition in the 2D spin ladder compound NaV2O5

Transient reflectance changes are studied for a spin ladder system α′-NaV2O5 in a temperature range from 4 K to room temperature, by means of femtosecond pump-and-probe measurements. A large response with a slow rise (3 ps) and a slow decay (>400 ps) is found only below 34 K, the phase transition temperature of charge ordering. The observed phenomena are ascribed to a photo-induced transition from the low-temperature phase to a state similar to the high-temperature phase.