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 (similar to 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.