Excitonic Resonance in Semiconductor-Metal Nanohybrids

We use a configuration interaction approach within the envelope function approximation to study the nature of the excitonic resonance in nanohybrids, composite nanoparticles (NPs) combining a semiconducting and a metallic segment in contact. With reference to recent experimental reports, we specifically study CdS-based nanorods with metallic NPs deposited at the tips (matchstick) or metallic coatings (core–shell). The excitonic states are computed taking into account both the renormalization of the electron–hole interaction and self-energy effects induced by the metallic segment on the electron–hole pair, as well as by the dielectric environment, through an induced charge numerical approach. In neutral matchstick structures, the metal NP has only a minor influence (1 meV) on the excitonic states. When the metallic NP is charged, the exciton becomes rapidly red-shifted and spatially indirect. In contrast, in neutral core–shell structures the exciton energy red-shifts by tens of millielectronvolts.