Ground state and non-linear excitations of two strongly coupled Su-Schrieffer-Heeger chains

A two-chain version of the original Su-Schrieffer-Heeger model with a strong interchain coupling is analysed for the case of a half-filled band, using a self-consistent iteration procedure and a continuum description in conjunction with bosonisation techniques. The problem of the stability of the iteration procedure is addressed and it is shown that the iteration converges to the (local) minima of the total ground state energy. The ground state of the present model is a trimerisation but also other homogeneous (metastable) phases are possible. The solitons in the model are of phason, amplitudon and intermediary type, but other more complicated solitons are also observed.