Period doubling in quasi-one-dimensional systems : A nonadiabatic approach

In this article we propose a new approach to the electron-phonon problem in partially filled bands. With the help of the ‘rotating wave approximation’ we derive a reduced hamiltonian that can partially be diagonalized analytically in a many-particle basis. Structurally different many-particle states show up. While in the conventional adiabatic treatment of quasi-one-dimensional systems already an arbitrary small electron-phonon coupling can lead to a Peierls-type distortion, within the here proposed formalism we may conclude that a critical coupling strength has to be overcome for an energy gap above the highest occupied state to occur.