Selection rule for the photoinduced phase transition dominated by anisotropy of strain in Ti3 O5

In photoinduced phase transitions, the relationship between the crystal orientation and the direction of the polarization or wave vector of light seems important, but surprisingly, such directional properties in photoinduced phase transitions have not been well studied experimentally. Ti3O5 exhibits a structural phase transition involving the anisotropic migration of Ti and O ions, and its nanocrystals exhibit a persistent photoinduced phase transition. We found that a photoinduced phase transition occurs even in a single crystal of this compound, but it significantly depends on the orientation of the plane on which the light is irradiated. Such a selection rule for photoinduced phase transitions is dominated by the anisotropy of the strain associated with the phase transition.