title: Exciton Formation and Quenching in a Au/CdS Core/Shell Nanostructure.
abstract: An atomistic description is presented of the excited state dynamics in spherical Au/CdS core/shell nanocrystals up to a diameter of 15 nm. Au-core excited states are considered in a multipole plasmon scheme, whereas a tight-binding description combined with a configuration interaction approach is used to compute single electron-hole pair excitations in the CdS-shell. The electron-hole pair energy-shift and screening due to an Au-core polarization is found of minor importance. For the studied system, the energy transfer coupling can be identified as the essential core-shell interaction. Characterizing the CdS-shell excitons by atomic centered transition charges and the Au-core by its multipole plasmon moments, an energy transfer coupling can be introduced that gives a complete microscopic description beyond any dipole-dipole approximation and with values around 10 meV. Together with a considerable plasmon-exciton energy mismatch, these coupling values explain the measured 300 ps lifetime of shell excitons due to energy transfer to the Au-core.
authors.affiliation: Institute für Physik, Humboldt-Universität zu Berlin , Netwonstraße 15, D-12489 Berlin, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Ziemannn
authors.affiliation: Institute für Physik, Humboldt-Universität zu Berlin , Netwonstraße 15, D-12489 Berlin, Germany.
authors.forename: Volkhard
authors.initials: V
authors.lastname: May
keywords: Coulomb correlated electron−hole pairs; core/shell nanocrystal; excitation energy transfer; excitons; multipole moments; plasmons; tight-binding model; transfer rates