Simulations of Plasmon-mediated Superradiance for Molecules in STM-based Nanocavity

Abstract

Scanning tunneling microscopy (STM) can be considered as a kind of nanocavity due to its main structure consisting of metallic tip and substrate, and the interaction between molecular clusters and plasmons can be controlled by moving the tip, thus changing their radiation. In this article, we apply the semi-classical method by combining macroscopic quantum electrodynamics theory with open quantum systems theory to calculate the transient radiation of the molecules arranged horizontally and vertically in the gap of the nanocavity. Our calculations show that the free-space field-mediated coherent coupling in the former case is about two orders of magnitude larger than the dissipative coupling. In contrast, in the latter case, the coherent coupling is cancelled by the contribution of the scattering field mediated by plasmons, and the dissipative coupling and molecular excitation are dramatically enhanced by the plasmons, which enables the possibility of generating fast superradiant pulses. We clarify the configuration to reach the plasmon-mediated superradiant pulses with the STM-based nanocavity and can guide further experiments in this direction.