Spin-charge separation in a model of two coupled chains.

A model of interacting electrons living on two chains coupled by a transverse hopping t⊥, is solved exactly by bosonization technique. It is shown that t⊥ does modify the shape of the Fermi surface also in presence of interaction, although charge and spin excitations keep different velocities uρ, uσ. Two different regimes occur: at short distances, x ≪ ξ = (uρ − uσ)/4t⊥, the two chain model is not sensitive to t⊥, while for larger separation x ≫ ξ inter–chain hopping is relevant and generates further singularities in the electron Green function besides those due to spin-charge decoupling.