Picocavity-Controlled Subnanometer-Resolved Single-Molecule Fluorescence Imaging and Mollow Triplets

Abstract

In this article, we address subnanometer resolved fluorescence imaging of single molecule inside a plasmonic picocavity by proposing a semiclassical theory via combining the macroscopic quantum electrodynamics theory and the open quantum system theory. To gain insights into the experimental results [Nat. Photonics202014694699], we have further equipped this theory with the classical electromagnetic simulation of the picocavity, formed by atomistic cluster-decorated silver STM tip and a silver substrate, and the time-dependent density functional theory calculation of zinc phthalocyanine molecule. Our simulations not only reproduce the fluorescence spectrum and imaging as measured in the experiment, confirming the influence of extreme field confinement afforded by the picocavity, but also predict Rabi oscillation dynamics and Mollow triplets spectrum for moderate laser excitation. Thus, our study highlights the possibility of coherently manipulating the molecular state and exploring quantum optical phenomena with the plasmonic picocavity.

Optomechanical effects in nanocavity-enhanced resonant Raman scattering of a single molecule

“…However, the molecular excitation saturates for strong laser excitation because of its two-level fermionic nature (in contrast to the infinite levels of a bosonic plasmon), and the SERRS signal saturates and even vanishes for strong laser excitation. In addition, we also find that the resonant fluorescence is redshifted by about 40 meV (plasmonic Lamb shift [29,30]), and broadened by about 22 meV (due to the Purcell effect), and also shows three broad peaks for strong laser excitation [31] (corresponding to the Mollow triplet similar to the situation in quantum optics [32]).…”

Optomechanical Effects in Nanocavity-enhanced Resonant Raman Scattering of a Single Molecule

“…However, the molecular excitation saturates for strong laser excitation because of its two-level fermionic nature (in contrast to the infinite-levels of a bosonic plasmon), and the SERRS signal saturates and even vanishes for strong laser excitation. In addition, we also find that the resonant fluorescence is red-shifted by about 40 meV (plasmonic Lamb shift [29,30]), and broadened by about 22 meV (due to the Purcell effect), and also shows three broad peaks for strong laser excitation [31] (corresponding to the Mollow triplet similar to the situation in quantum optics [32]).…”

Analysis by nonlocal response theory of tip-enhanced photoluminescence image of a single molecule

“…In the previous study on the theory of TEPL, the frequency in the Green's function is fixed to the transition frequency of the molecule in the literature [5]. On the other hand, the Green's function in our theory is a function of frequency, and hence, we can correctly calculate photoluminescence even in the situation where the resonance level of the molecule shifts or splits due to the strong coupling between the gap plasmons sustained at the metal probe tip and the molecule.…”