2002 年 23 巻 11 号 p. 695-701
Photoinduced phase transitions via excited electronic states are discussed theoretically using a one-dimensional model composed of localized electrons and lattices under the adiabatic or diabatic approximation. We show that the global phase change by photoexcitation only at a site is possible, and we clarify conditions for the occurrence of such phenomena. In the adiabatic regime, depending on the intersite interaction, an initial local photoinduced change (i) remains locally, (ii) induces cooperatively a global phase change, or (iii) disappears and the system returns to the initial phase. Dynamical features of the case (ii) are characterized by the “deterministic domino” processes of the domain walls; the domain walls between the two phases move deterministically with a constant velocity without spontaneous emissions. In the diabatic regime, similar three types of photoinduced change are possible. The domain-wall dynamics is described as the “stochastic domino” process with a random velocity, which is accompanied by the successive radiative transitions. Related topics of the photoinduced domino theory are also introduced.