Visualizing hybridized quantum plasmons in coupled nanowires: From classical to tunneling regime

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 Å the energy dispersion of the modes deviate from classical results due to the onset of weak tunneling. Below 2-3 Å 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.

A generalized non-local optical response theory for plasmonic nanostructures

“…Re-introducing the diffusion constant and 34 . In support of our prediction of diffusive broadening, recent RPA studies reveal an increased plasmon linewidth associated with Landau damping 35 , that is, electron-hole pair excitation near the surface of nanostructures as also observed in studies based on timedependent density functional theory (TD-DFT) 36 . We provide in the following two key examples of the GNOR approach, demonstrating that the interplay of quantum pressure and diffusion has a remarkable impact on the optical response of plasmonics nanostructures and solving long-standing open problems.…”

“…Ab initio approaches show a crossing from the classical hybridization of localized surface plasmon resonances to tunnelling-mediated charge-transfer plasmons (CTPs) 36,[48][49][50] . Being able to push experiments into this intriguing regime 13,30,51 , commonly associated with expectations of quantum physics, leaves an open question: Can this regime be adequately described with semiclassical models?…”

Hyperbolic metamaterial lens with hydrodynamic nonlocal response

“…Similar nonlocal blueshifts for single nanoplasmonic particles have been predicted before, and significant blueshifts have also been measured [27,29]; how much of these can be attributed to hydrodynamic effects is a hot topic [27,29,35]. Similar discussions apply to nanowire dimers [36][37][38].…”

Ab initionanoplasmonics: The impact of atomic structure

“…These effects can be incorporated into Maxwell equations in an approximate manner using, e.g., nonlocal dielectric functions [13][14][15][16][17][18][19] or the ad hoc inclusion of "virtual" dielectric materials [20][21][22]. While these semiclassical approximations have been successfully applied in many cases, they do not achieve the precision provided by first-principle calculations.A number of recent publications [20,[23][24][25][26][27] have treated the electronic response of plasmonic structures using stateof-the-art time-dependent density functional theory (TDDFT) [28,29]. However, the ionic structure is typically neglected and replaced by a homogeneous jellium background or by an unstructured effective potential.…”

“…A number of recent publications [20,[23][24][25][26][27] have treated the electronic response of plasmonic structures using stateof-the-art time-dependent density functional theory (TDDFT) [28,29]. However, the ionic structure is typically neglected and replaced by a homogeneous jellium background or by an unstructured effective potential.…”