Nanoparticle heterodimers: The role of size and interparticle gap distance on the optical response

Highlights: • Composite nanostructures with controlled size, shape and relative arrangement is a subject of significant research interest. • Using TDDFT calculations, we investigate how the optical response modify in Al homodimers and heterodimers. • Heterodimers show more complex optical response evolution due to a symmetry-breaking in the system. Composite plasmonic nanostructures with controlled size, shape and relative arrangement is a subject of significant current research interest. Much of this is stimulated by the prospects by generating enormous near-field enhancements of the surface and interparticle gap regions for potential applications in surface-enhanced spectroscopies. In this manuscript, using time-dependent density functional theory (TDDFT) calculations, we investigate how the optical response in size matched homodimers and size mismatched heterodimers composed of Aluminum modify while varying the size and interparticle gap distances in the sub-nanometer range. Both systems show interesting optical response evolution. In particular, the size mismatched heterodimers show even more complex optical response evolution due to a symmetry-breaking in the system.