A modeling study of multilayer nanowires finds that, in its calculations, shifting a shell off center moves plasmonic hot spots—small regions where the near electric field is concentrated—toward thinner shell sections. The result connects shell alignment to the spatial distribution of the modeled optical field.
The document is an arXiv version 1 preprint dated 26 August 2026. It examines how shell nonconcentricity changes the quasistatic optical response of core–single-shell and core–multi-shell nanowires, focusing on resonance, absorption and near-field behavior.
A geometry with consequences
The modeled systems are infinitely long nanowires with cross-sectional dimensions ranging from a few to several tens of nanometers. The nonconcentric interfaces are described with bipolar coordinates.
For the nonconcentric cylindrical interfaces, the study derives analytical solutions in bipolar coordinates and uses them to analyze resonance, absorption and near-field behavior. For larger bull’s-eye wires, concentric structures are calculated with analytical Mie theory, while nonconcentric structures are handled with the discontinuous Galerkin time-domain, or DGTD, finite-element method.
Together, these methods provide a quasistatic analytical treatment of nonconcentric interfaces and a full-wave numerical comparison for larger bull’s-eye wires. The findings concern the modeled response of those geometries.
In core–single-shell structures, increasing displacement concentrates the induced field in and around the thinnest part of the shell. As the nonconcentricity grows, the calculated plasmonic hot spots progressively shift toward thinner shell regions.
More modes, more branches
Nonconcentricity also changes which modes can couple to light. Higher-order plasmon modes that are dark in the quasistatic concentric limit have finite optical coupling in the nonconcentric geometry.
In the tube-wire cavity, modified shell resonances split into two hybridized branches. One is a low-frequency bonding branch; the other is a high-frequency antibonding branch.
Additional metal–dielectric interfaces broaden the spectral response, while nonconcentric geometries increase the density of accessible resonances. In ordinary terms, the modeled structure responds across a broader collection of resonant features, with more of those features available to optical excitation.
That access is not unlimited. At the intersection, or crescent, limit, scattered-field amplitudes vanish, indicating that localized surface plasmons can no longer be efficiently excited.
A computational cross-check
The full-wave comparison provides a numerical check near isolated-cylinder resonances. In the bipolar case, relative deviations stayed below 10% for absorption and 5% for scattering. In the Doppler-grating-inspired comparison, deviations stayed below 5% for both absorption and scattering.
For the concentric bull’s-eye wire, DGTD results were described as accurately reproducing the absorption and scattering efficiencies calculated with cylindrical Mie theory. The reported agreement is between two computational approaches within the modeled system.
The boundary of the model
The main limitation is the quasistatic approximation used for the analytical results. The authors state that it overestimates near-field enhancements and absorption efficiencies at plasmonic resonances, so the discussion emphasizes resonance frequencies and spatial field distributions.
The geometric scope is also explicit: the central models describe infinitely long wires. The authors identify nonlocal response, finite wire height and comparisons involving Doppler-grating-inspired nanodisks as future extensions.
The authors report financial support from the German Research Foundation through Collaborative Research Center 1375, Project ID 398816777, and Projects A6 and C1.
Paper data and sources
Original title: Nonconcentric Multi-shell Nanowires: Geometry-Induced Plasmon Hybridization and Near-Field Localization
Authors: Gino Wegner, Jer-Shing Huang, Kurt Busch
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-26
DOI: Not available
Original paper · Full text