Theoretical study of polarons and self-trapped excited states in one-dimensional C₆₀ crystal

The role of electron correlation, conjugation of π-electrons on formation of polarons and excitons in C₆₀ solids has been investigated. For description of the polaron and exciton we use a generalized Su-Shrieffer-Heeger (SSH) model for the intermolecular and intramolecular degrees of freedom including a Hubbard-type on-site interaction. It is shown that in the case of a linear chain with one extra electron (hole), for weak π-conjugation a polaron is generated. In the case of the electron excitation from the highest occupied state in the upper valence band to the lowest unoccupied state in the lower conductance band, a Frenkel exciton is formed on the central C₆₀ molecule in the supercell at small conjugation parameter. The formation of the charge-transfer exciton is observed in the case of the electron excitation from the highest occupied state in the upper valence band to the third lowest unoccupied state in the lower conduction band.