Semiconductor-metal nanoparticle molecules in a magnetic field: Spin-plasmon and exciton-plasmon interactions

Excitons and plasmons in hybrid semiconductor-metal nanostructures strongly interact via the Coulomb forces. Simultaneously, excitons in semiconductors experience typically strong intrinsic spin-dependent interactions that result in efficient coupling between spins of excitons and dynamic electric fields of photons. A joint action of the exciton-plasmon and spin-dependent interactions leads to a coupling between spins and plasmons. Calculated optical spectra of hybrid nanoparticle molecules reveal such spin-plasmon coupling. The spin-plasmon coupling creates spin-dependent Lamb shifts of excitons. In the presence of the exciton-plasmon interaction, the spin splitting in the exciton spectrum can decrease or even vanish under certain conditions. In a magnetic field, the spin-plasmon interaction strongly alters optical spin-dependent selection rules, leading to forbidden optical lines. Allowed and forbidden optical transitions in the presence of the exciton-plasmon and spin-plasmon interactions typically acquire Fano-type or antiresonance shapes. Plasmon-induced interactions in semiconductor-metal nanocrystal structures suggest interesting opportunities for tailoring of spin and optical spectra of excitons.