Quantum Many-Body Effects in the Optoelectronic Response of Plasmonic Nanostructures and their Coupling to Quantum Emitters

Abstract

This thesis theoretically addresses the optoelectronic response of metallic nanoparticles (MNPs) as well as their coupling to quantum emitters (QEs). Nanometer-scale systems are considered where optical nonlinearity, nonlocality, or electron-transfer processes can all play an important role. To capture these quantum many-body effects, Time-Dependent Density Functional Theory (TDDFT) is used primarily, in combination with semiclassical models based on the Surface-Response Formalism (SRF) and classical calculations based on the Local-Response Approximation (LRA). We demonstrate that, at the nanometer scale, electron spill-out and surface-enabled Landau damping drastically influence the electromagnetic interaction between MNPs and QEs, which produce a redshift and broadening of plasmonic resonances not captured by classical theories. We show that these effects can be correctly described by the semiclassical SRF, in particular when one considers the nonlocal response in the direction parallel to the metal surface. In addition, we predict that the hybridization between the electronic states of the QE and those of the MNPs drastically modifies the optical response of the coupled system in situation involving subnanometric distances, since the exciton in the QE is found to be quenched due to electronic coupling. This quenching dramatically influences the frequency and the width of the optical resonances sustained by the coupled structure. Finally, we demonstrate that the electromagnetic coupling of a QE to a spherical MNP can also affect the nonlinear optical response of the system, enabling otherwise-forbidden second-harmonic generation (SHG).