On the linear response and scattering of an interacting molecule-metal system

TL;DR

This paper develops a Green's function-based microscopic theory to analyze the coupling and response of molecule-metal systems in plasmon-enhanced spectroscopy, revealing detailed quantum interactions and resonance shifts.

Contribution

It introduces a self-consistent quantum-molecular response framework integrated into electromagnetic scattering calculations for molecule-metal systems.

Findings

Explicit computation of electronic Green's functions captures molecule-metal interactions.

The approach predicts resonance wavelength shifts from first principles.

Finite lifetimes and state shifts are naturally incorporated into the model.

Abstract

A many-body Green's function approach to the microscopic theory of plasmon-enhanced spectroscopy is presented within the context of localized surface-plasmon resonance spectroscopy and applied to investigate the coupling between quantum-molecular and classical-plasmonic resonances in monolayer-coated silver nanoparticles. Electronic propagators or Green's functions, accounting for the repeated polarization interaction between a single molecule and its image in a nearby nanoscale metal, are explicitly computed and used to construct the linear-response properties of the combined molecule-metal system to an external electromagnetic perturbation. Shifting and finite lifetime of states appear rigorously and automatically within our approach and reveal an intricate coupling between molecule and metal not fully described by previous theories. Self-consistent incorporation of this quantum-molecular response into the continuum-electromagnetic scattering of the molecule-metal target is exploited to compute the localized surface-plasmon resonance wavelength shift with respect to the bare metal from first principles.