Hybridization of quantum plasmon modes in coupled nanowires: From the classical to the tunneling regime

TL;DR

This study uses quantum mechanical calculations to analyze how plasmon modes in coupled nanowires transition from classical behavior to quantum tunneling effects as the separation decreases.

Contribution

It provides a detailed quantum description of hybridized plasmon modes in nanowires, capturing the transition from classical to tunneling regimes using TDDFT.

Findings

Plasmon energies deviate from classical predictions at small radii and high momentum transfer.

Hybridized modes change shape with decreasing separation, showing quantum effects.

Charge-transfer plasmons emerge below 2-3 Å, indicating strong tunneling.

Abstract

We present full quantum mechanical calculations of the hybridized plasmon modes of two nanowires at small separation, providing real space visualization of the modes in the transition from the classical to the quantum tunneling regime. The plasmon modes are obtained as certain eigenfunctions of the dynamical dielectric function which is computed using time dependent density functional theory (TDDFT). For freestanding wires, the energy of both surface and bulk plasmon modes deviate from the classical result for low wire radii and high momentum transfer due to effects of electron spill-out, non-local response, and coupling to single-particle transitions. For the wire dimer the shape of the hybridized plasmon modes are continuously altered with decreasing separation, and below 6 {\AA} the energy dispersion of the modes deviate from classical results due to the onset of weak tunneling. Below 2-3 {\AA} separation this mode is replaced by a charge-transfer plasmon which blue shifts with decreasing separation in agreement with experiment, and marks the onset of the strong tunneling regime.