Collective modes in tunneling quantum-dot arrays

We present a theoretical study of the collective excitations and optical response of two-dimensional arrays of quantum dots. We calculate the dispersion curves and oscillator strength for the various modes when tunneling between nearest-neighbor dots is considered. The self-consistent-field formalism and a Wannier representation, described in the tight-binding approximation, is used to study the behavior of the modes of the system for different lattice parameters. We show that a band of interdot tunneling modes appears due to carrier tunneling between neighbors. The relative oscillator strength of the various interband and intraband excitation modes is calculated from the density-density correlation function. The tunneling modes are found to have a nonvanishing strength, possibly detectable in experiments.