Conversion of excitons to spin-soliton pairs in quasi-one-dimensional halogen-bridged metal complexes

We have characterized the gap states from photoinduced absorption and photoinduced ESR studies on one-dimensional (1D) halogen-bridged metal complexes with degenerate and nondegenerate charge density wave (CDW) ground state. A comparison of excitation profiles of self-trapped exciton (STE) luminescence with those of the gap states demonstrates that excitons are relaxed to spin-soliton pairs. From an analysis of the temperature dependence of luminescence decay time, conversion from the STE to the solitonic state is found to occur through a finite potential barrier, the magnitude of which strongly depends on the degeneracy of the CDW.