Ultrafast dynamics of a photoinduced phase transition in single-crystal trititanium pentoxide

We investigate photoinduced phase transition of Ti3O5 using the pump-probe method in an ultrafast electron microscope. We measured time-resolved electron diffraction patterns of single-crystal lamellae of Ti3O5 excited by the femtosecond laser at the wavelength of 800 and 400 nm. Under 800 nm laser excitation, the photoinduced phase transition from the beta-phase to the lambda-phase with a similar timescale to previous measurements conducted using nanocrystals was observed. This indicates that the photoinduced phase transition is not a phenomenon influenced by the material surface, size, or boundary, but an intrinsic property in a bulk crystal of Ti3O5. The photoinduced phase transition was not detected, when excited by the laser at the wavelength of 400 nm. The results are discussed based on the electronic states of beta- Ti3O5 and lambda- Ti3O5. The density of the dissociated interatomic bonds between Ti at the specific site should be an important factor for triggering the photoinduced phase transition.