  Collective excitations in topologically non-trivial systems have attracted
considerable attention in recent years. Here we study plasmons in the
Su-Schrieffer-Heeger model whose low-energy electronic band is only partially
filled, such that the system is metallic. Using the random phase approximation,
we calculate the intra- and inter-band polarization functions and determine the
bulk plasmonic dispersion from the dielectric function within the random phase
approximation. We find that the sub-lattice basis states strongly affect the
polarization functions and therefore control the system's plasmonic
excitations. By varying the real-space separation of these local orbitals, one
can thus selectively enhance or suppress the plasmonic energies via a tunable
trade-off between intra-band and inter-band screening processes. Specifically,
this mechanism can be used to stabilize undamped high energy plasmons that have
already been reported in related models. We propose scenarios on how to control
and observe these effects in experiments.
