The Indirect Excitons Contribution to the Polarizability of a Dielectric Nanoparticle

The optical properties of dielectric nanostructures strongly depend on dielectric nanoparticles (NP) polarizability which can take the high values even interacting with low-intensity radiation. In this article, we are trying to find out if this is possible for electron transits to indirect exciton (IX) states at the NP surface. Because the exciton energy spectrum depends on NP shape and size, we research these factors influence on NP polarizability within the dipole approximation framework. For a quantitative assessment, we use a nanosystem containing a spherical dielectric alumina nanoparticle in a dielectric medium with a lower permittivity. We estimated the impact of NP size effect on the NP energy spectrum and the NP polarizability in case of exciton transitions to spatially separated electron and hole condition at the interface of dielectric nanoparticle and dielectric medium. Thus, using the variational method, we found that NP polarizability can achieve many orders of magnitude higher values than for atomic and molecular electron transitions case. It’s take place for infrared, visible and ultraviolet radiation ranges. Also was found that size-dependence of IE energy spectrum weakly affects on NP polarizability. The obtained results can be used for creating the nano- and heterostructures for advanced nanophotonic applications that operate in conditions of weak optical fields.