Electronic excitations in cylinder superlattices

A cylinder superlattice is formed by arranging the same hollow tubules in a linear lattice. Excitation properties are studied by evaluating the dielec tric function within the linear-response approximation. The electronic exci tations of a cylinder superlattice are the superposition of those of the in dividual tubules. However; these two systems an very different from each ot her. The excitations of different transferred angular momenta (L's) are gen erally coupled in the former, while they are decoupled in the latter. a cyl inder superlattice has a highly anisotropic structure, so the electronic ex citations strongly depend on the magnitude (q) and the direction (theta) of the transferred momentum. It might exhibit two plasmon branches. The low- and high-frequency plasmons, respectively, come from the L=0 and L=1 collec tive excitations in all tubules. Whether they could exist is determined by q and theta. The comparison among multi-cylinder systems, cylinder superlat tices, and cylinder bundles shows that they, respectively, exhibit one-, tw o-. and three-dimensional characteristics in the collective excitations, e. g., the q-dependence of the plasmon frequency. This important difference is caused by the different Coulomb interactions.