Plasmons in a quasi-one-dimensional metal in the random-phase and screened-Hartree-Fock approximations

Abstract

We consider plasmons in a lattice with chain structure. The electrons are treated in a one-band tight-binding model. From the corresponding longitudinal dielectric matrix ${\ensuremath{\epsilon}}_{G{G}^{\ensuremath{'}}}(q\ensuremath{\omega})$ the plasmon dispersion is determined in the random-phase approximation and in the screened-Hartree-Fock approximation. In comparing these results we find a remarkable decrease of the short-wavelength part of the plasmon dispersion relative to the long-wavelength limit, caused by the exchange corrections. The inclusion of overlap matrix elements is important for bands which are not half-filled. Furthermore, this inclusion of overlap is a necessary but not sufficient precondition for the existence of a second acoustical plasmon branch in our model.