Resonant interaction of molecular vibrations and surface plasmon polaritons: The weak coupling regime

TL;DR

This paper investigates how tuning surface plasmon frequencies in ZnO:Ga semiconductors into resonance with molecular vibrations affects the spectral signatures, revealing phase-sensitive interactions in the weak coupling regime.

Contribution

It demonstrates the phase-sensitive perturbation of surface-plasmon-polariton generation caused by molecular vibrations in the weak coupling regime.

Findings

Distinct spectral signatures at vibrational frequencies

Line shape changes from absorptive to anti-resonance

Phase-sensitive perturbation of surface plasmons

Abstract

Adjusting the free-electron concentration, the surface plasmon frequency of the semiconductor ZnOGa is tuned into resonance with the molecular vibrations of the n-alkane tetracontane. Closed molecular films deposited on the semiconductor's surface in the monolayer regime generate distinct signatures in total-attenuated-reflection spectra at the frequencies of the symmetric and asymmetric stretching vibrations of the CH2 group. Their line shape undergoes profound changes from absorptive to dispersive and even anti-resonance behavior when moving along the surface- plasmon dispersion by the angel of incidence. We demonstrate that this line shape diversity results from a phase-sensitive perturbation of the surface-plasmon-polariton generation at the molecule/metal interface.