Electron self-trapping on a nanocircle

We study the self-trapping of quasiparticles (electrons, holes or excitons) in a molecular chain with the structure of a ring, taking into account the electron–phonon interaction and the radial and tangential deformations of the chain. A discrete system of equations is obtained and solved numerically. The analytical solutions for the wavefunction of a quasiparticle and for the molecule displacements that determine the distortion of the ring are also investigated. The numerical solutions of the system of discrete nonlinear equations, as well as analytical solutions, reveal several regimes of quasiparticle localisation in the chain. These regimes depend on the values of the parameters of the system. It is shown that for strong enough coupling between a quasiparticle and phonons, the transverse deformation of the nanocircle favours the formation of a soliton.