Dynamics of solitons and polarons in the quasi-one-dimensional MX chain compound [Pt(en${)}_2$ ][Pt(en${)}_2$ ${\mathrm{I}}_2$ ](${\mathrm{ClO}}_4$ ${)}_4$s

The dynamics of solitons and polarons have been studied in a [Pt(en${)}_2$ ][Pt(en${)}_2$ ${\mathrm{I}}_2$ ](${\mathrm{ClO}}_4$ ${)}_4$ single crystal using photoinduced infrared absorption measurements. The annihilation process of the gap states is well explained by the bimolecular recombination model. Both carriers are long lived at low temperatures due to their finite pinning energies, and their decay characteristics are strongly temperature dependent. The temperature dependences of the rate constant of recombination for both carriers clearly show a crossover of the transport mechanism from hopping to tunneling with decrease of temperature. This behavior of the gap states is in contrast to that observed in transpolyacetylene.