Competition between Local Field Enhancement and Nonradiative Resonant Energy Transfer in the Linear Absorption of a Semiconductor Quantum Dot Coupled to a Metal Nanoparticle

In this work, we systematically investigate the linear absorption associated with the excitons' interband transition of a semiconductor quantum dot (SQD) in proximity to a metal nanoparticle (MNP), where the competition between local field enhancement and nonradiative resonant energy transfer (NRET) plays a critical role. It is shown that the linear absorption coefficient of the SQD depends strongly on the geometrical parameters of the hybrid nanostructure. In particular, a continuous transition from absorption enhancement to quenching with varying MNP size and SQD location is clearly observed. Three regimes are identified unambiguously where NRET or local field enhancement governs the absorption response of the SQD in the hybrid nanostructure. In the first regime, where the separation distance between the SQD and the MNP is relatively short and the SQD-MNP coupling is strong, the dominant contribution to the absorption response of the SQD is the NRET effect, and the multipole effect must be considered in addition to the dipole effect. As the separation distance between the SQD and the MNP increases, the coupling is slightly weakened, and the local field enhancement becomes the dominant contribution to the optical response of the SQD in the second regime. When the coupling is further weakened by increasing the distance between the SQD and the MNP, the strong coupling interaction is diminished, and the optical response approaches the case of the bare SQD. Controlling the geometrical parameters of the nanostructure not only provides a further engineering degree of freedom to elucidate the underlying physics of these structures, but also offers a general guide for the optimal design of SQD-MNP hybrid nanostructures toward novel optoelectronics applications.