Surface Plasmon Polariton Modified Exciton De-excitation in Quantum Dot*

We report theoretically a full quantum mechanical study for a prototypical system composed of a spherical quantum dot (QD) close to a metal surface. Due to the excitation of surface plasmon polaritons (SPPs), the strong electromagnetic fields near the metal surface are expected to modify the de-excitation rate of the quantum dot. Through the development of a new theoretical model with quantized SPP, we find that the de-excitation rate of the exciton in quantum dots can be modified by controlling both the crystal orientation and size of the QD. Most importantly, the quantization of the SPP enables us to find that although the radiative de-excitation of the spherical quantum dot should satisfy the quantum selection rule of the angular momentum, a new selection-rule forbidden de-excitation channel is open up due to the SPP and exciton coupling. The quantum interference between the new and the conventional selection-rule allowed channels can dramatically modify the total de-excitation rate of the exciton. Our theoretical predictions of technological importance can be readily tested experimentally, and are expected to guide new strategies to advance the quantum-dot-based applications by combining the QD and systems supporting SPPs.