Collective multipole oscillations direct the plasmonic coupling at the nanojunction interfaces

Area of Science:

• Plasmonics
• Nanoparticle Spectroscopy
• Optical Properties of Materials

Background:

• Plasmonic coupling in nanoparticle dimers is typically described by dipolar interactions.
• Existing models like the plasmonic ruler equation may not fully capture complex coupling behaviors.
• Higher-multipolar order plasmon modes are often overlooked in spectral response analyses.

Purpose of the Study:

• To systematically investigate the impact of higher-multipolar order plasmon modes on silver nanoparticle dimer spectral response.
• To introduce and describe a refined coupling mechanism that accounts for these higher-order modes.
• To analyze the sensitivity of plasmonic coupling to particle geometry and separation distance.

Main Methods:

• Systematic theoretical study of silver nanoparticle dimers.
• Detailed calculations of plasmonic coupling, considering contributions beyond primary bands.
• Analysis of spectral response and coupling mechanisms for cubic and spherical nanoparticles.

Main Results:

• Plasmonic coupling is influenced by higher-order modes, not just the main dipolar band.
• The decay length of higher-order modes is sensitive to interparticle distance and gap size.
• Cubic and larger spherical nanoparticles exhibit significant higher-order mode contributions, affecting coupling even at larger separations.

Conclusions:

• A more comprehensive understanding of plasmonic coupling requires considering higher-multipolar order modes.
• The proposed mechanism refines the plasmonic ruler equation for specific nanoparticle geometries.
• Higher-order modes play a critical role in the spectral response and coupling behavior of silver nanoparticle systems.