Polarons inC60

Abstract

A simple Su-Schrieffer-Heeger-type model of ${\mathrm{C}}_{60}$ and doped ${\mathrm{C}}_{60}$ is presented. The model is solved numerically in the adiabatic approximation. In the half-filled case the cluster dimerizes, in agreement with experiment and more complicated calculations. When an electron is added to half-filling, a polaron is present in the ground state. This polaron possesses an unusual geometry; it is a loop circling the ${\mathrm{C}}_{60}$ cluster. For two added electrons a bipolaron forms with a similar geometry. It is suggested that this bipolaron may be observable in optical experiments.