Accelerated motion of photo-induced phase boundary in one-dimensional systems

Numerical calculation of photo-induced structural phase transitions is carried out for one-dimensional systems, which have two potential-energy minima for an atom in the ground state and one minimum in an excited electronic state, the system being initially in a metastable state. The dynamics of the atomic transitions into new minima after photo-excitation is studied by a molecular dynamical method to clarify how the energy released after an atom moves from one minimum to another transfers effectively to the next atom. During an initial period of new phase development, an accelerated motion of a phase boundary takes place. Its velocity becomes large and exceeds the group velocity of phonons in both phases. Such situations may be realized in the case of small friction in the domino model [K. Koshino, T. Ogawa, Phys. Rev. B, 58 (1998) 14 804].