Pair-creation path of doubly charged spinless soliton through photoexcitation in halogen-bridged metal complexes

Abstract

To clarify the lattice relaxation paths of the photo-generated charge transfer excitation in halogen-bridged mixed-valence metal complexes, we study the ground and excited states of a one-dimensional Peierls-Hubbard model with half-filled electrons. A pair of doubly charged solitons is shown to be the lowest excited state and causes a photo-induced absorption (PIA) with an energy of about half of the gap, while a distant pair of polarons is shown to give the PIA observed by Kurita et al. The self-trapped exciton is shown to be next lowest excited state separated from this soliton pair only by a small barrier in agreement with the recent experiments.