Gap states of polaron and associated optical absorption in the quasi-one-dimensional solid (Pt(en)2)(PtCl2(en)2)(ClO4)4

Abstract

The energy spectrum and the optical absorption coefficient alpha ( omega ) of a hole polaron in a PtCl chain are numerically calculated on the basis of the Baeriswyl-Bishop model. In intermediate coupling, there appear some shallow gap states as well as deep gap states, both of which give contributions to the absorption. The three-band structure of the absorption in the near- and mid-infrared region is consistent with the experimental data on (Pt(en)2)(PtCl2(en)2)(ClO4)4. The theory also shows that in the far-infrared region there is another absorption near 500 cm-1, which is associated with the shallow gap states.