Photogeneration of Solitons and Polarons in MX Chains

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Abstract
The effects of the electron-lattice (e-1) coupling and the interchain interaction on the gap states in the one-dimensional Peierls-Hubbard system have been investigated by the photo-induced absorption (PA) measurements of the halogen-bridged metal complexes (the MX chains; M=Pt and X=Cl, Br or I). In the complexes having small amplitude of CDW, three PA bands named a1 , a2 and b are observed. The PA bands a1 and a2 , which are insensitive to the interchain interaction, are assigned to polarons. The decrease of the interchain coupling of CDW leads to a midgap band b, which is attributable to charged-solitons. While, in the complexes having large amplitude of CDW, there are observed the two PA bands A and B having the long life time. Spectral shapes and excitation profiles of these PA bands are considerably different from those of the a1 , a2 and b bands. These results suggest that generation processes and stabilization energies of the gap states are strongly dependent on the magnitude of e-1 interactions.