Photoinduced Phase Transition in Charge Order Systems-Charge Frustration and Interplay with Lattice

Lattice effects on photoexcited states in an interacting charge-frustrated system are examined. Real-time dynamics in the interacting spinless fermion model on a triangular lattice coupled to lattice vibration are analyzed by applying the exact diagonalization method combined with the classical equation of motion. A photoinduced phase transition from the horizontal stripe-type charge order (CO) to the 3-fold CO occurs through a characteristic intermediate time domain. By analyzing the time evolution in detail, we find that these characteristic dynamics are seen when the electron and lattice sectors are not complementary to each other but show cooperative time evolutions. The dynamics are distinct from those from the vertical stripe-type CO, in which a monotonic CO melting occurs. A scenario of the photoinduced CO phase transition with lattice degree of freedom is presented from the viewpoint of charge frustration.