  A theory for the collective plasma excitations in a linear periodic array of
spherical two-dimensional electron gases (S2DEGs) is presented. This is a
simple model for an ultra thin and narrow microribbon of fullerenes or metallic
shells. Coulomb coupling between electrons located on the same sphere and on
different spheres is included in the random-phase approximation (RPA). Electron
hopping between spheres is neglected in these calculations. The resulting
plasmon-dispersion equation is solved numerically. Results are presented for a
superlattice of single-wall S2DEGs as a function of the wave vector. The
plasmon dispersions are obtained for different spherical separations. We show
that the one-dimensional translational symmetry of the lattice is maintained in
the plasmon spectrum. Additionally, we compare the plasmon dispersion when the
superlatice direction is parallel or perpendicular to the axis of quantization.
However, because of anisotropy in the Coulomb matrix elements, there is
anticrossing in the plasmon dispersion only in the direction perpendicular to
the quantization axis. The S2DEG may serve as a simple model for fullerenes,
when their energy bands are far apart.
