Spatial nonlocality in the infrared absorption spectra of polar semiconductor nanospheres

The absorption of infrared radiation by a polar semiconductor nanosphere is investigated, using a new extension of the Mie theory. The theory takes into account the spatial dispersion or nonlocality and determines the generalized Mie coefficients using an additional boundary condition of the continuity of the normal component of the displacement field at the surface of the system. Examples of calculated infrared absorption spectra are presented, by employing the typical values of doped InAs and InSb nanospheres. In the presence of the spatial nonlocal effects, the blue shift of the main absorption peaks, due to the coupled surface plasmon-optical phonon modes, are found to occur, while two groups of subsidiary peaks, due to coupled bulk plasmon-optical phonon excitations, appear in the optical spectra of the polar semiconductor nanospheres. (paper)