Topological edge plasmon modes between diatomic chains of plasmonic nanoparticles (original) (raw)
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Plasmonic Topological Edge States between Diatomic Chains of Nanoparticles
We study the topological edge plasmon modes between two "diatomic" chains of identical plasmonic nanoparticles. Zak phase for longitudinal plasmon modes in each chain is calculated analytically by solutions of macroscopic Maxwell's equations for particles in quasi-static dipole approximation. This approximation provides a direct analogy with the Su-Schrieffer-Heeger model such that the eigenvalue is mapped to the frequency dependent inverse-polarizability of the nanoparticles. The edge state frequency is found to be the same as the single-particle resonance frequency, which is insensitive to the separation distances within a unit cell. Finally, full electrodynamic simulations with realistic parameters suggest that the edge plasmon mode can be realized through near-field optical spectroscopy.
Plasmonic modes in periodic metal nanoparticle chains: a direct dynamic eigenmode analysis
Optics Letters, 2007
We demonstrate an efficient eigen-decomposition method for analyzing the guided modes in metal nanoparticle chains. The proposed method has the advantage of showing the dispersion relation and mode quality simultaneously. It can also separate the material and geometrical properties, so its efficiency does not depend on the complexity of the material polarizability. The method is applied to analyze the guided modes of a single and a pair of metal chains. The more accurate dynamic dipole polarizability typically gives a red-shift compared with the results obtained with the broadly used quasistatic dipole polarizability with radiation correction.
The Birth of a Plasmonic Topological Quasiparticle on the Nanofemto Scale
arXiv: Mesoscale and Nanoscale Physics, 2019
At interface of the classical and quantum physics Maxwell and Schrodinger equations describe how optical fields drive and control electronic phenomena at THz or PHz frequencies and on ultra-small scales to enable lightwave electronics. Light striking a metal surface triggers electric field-electron particle/wave interactions to coherently imprint and transfer its attributes on the attosecond time scale. Here we create and image by ultrafast photoemission electron microscopy a new quasiparticle of optical field-collective electron interaction where the design of geometrical phase creates a plasmonic topological spin angular momentum texture. The spin texture resembles that of magnetic meron quasiparticle, is localized within 1/2 wavelength of light, and exists on ~20 fs (2^10-14 s) time scale of the plasmonic field. The quasiparticle is created in a nanostructured silver film, which converts coherent linearly polarized light pulse into an evanescent surface plasmon polariton light-el...
Collective plasmon modes in a compositionally asymmetric nanoparticle dimer
2011
The plasmon coupling phenomenon of heterodimers composed of silver, gold and copper nanoparticles of 60 nm in size and spherical in shape were studied theoretically within the scattered field formulation framework. In-phase dipole coupled σ -modes were observed for the Ag-Au and Ag-Cu heterodimers, and an antiphase dipole coupled π -mode was observed for the Ag-Au heterodimer. These observations agree well with the plasmon hybridization theory. However, quadrupole coupled modes dominate the high energy wavelength range from 357-443 nm in the scattering cross section of the D=60 nm Ag-Au and Ag-Cu heterodimer. We demonstrate for the first time that collective plasmon modes in a compositionally asymmetric nanoparticle dimer have to be predicted from the dipole-dipole approximation of plasmon hybridization theory together with the interband transition effect of the constitutive metals and the retardation effect of the nanoparticle size. Copyright 2011 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License.
Physical Review B, 2004
We calculate the surface-plasmon dispersion relations for a periodic chain of spherical metallic nanoparticles in an isotropic host, including all multipole modes, in a generalized tight-binding approach. For sufficiently small particles (kdӶ1, where k is the wave vector and d is the interparticle separation͒, the calculation is exact. The lowest bands differ only slightly from previous point-dipole calculations provided the particle radius aՇd/3, but differ substantially at smaller separation. We also calculate the dispersion relations for many higher bands, and estimate the group velocity v g and the exponential decay length D for energy propagation for the lowest two bands due to single-grain damping. For a/dϭ0.33, the result for D is in qualitative agreement with experiments on gold nanoparticle chains, while for smaller separation, such as a/dϭ0.45, v g and D are expected to be strongly k dependent because of the multipole corrections. When the particles touch, we predict percolation effects in the spectrum, and find surprising symmetry in the plasmon band structure. Finally, we reformulate the band-structure equations for a Drude metal in the time domain, and suggest how to include localized driving electric fields in the equations of motion.
Nonradiative limitations to plasmon propagation in chains of metallic nanoparticles
Physical Review B
We investigate the collective plasmonic modes in a chain of metallic nanoparticles that are coupled by nearfield interactions. The size-and momentum-dependent nonradiative Landau damping and radiative decay rates are calculated analytically within an open quantum system approach. These decay rates determine the excitation propagation along the chain. In particular, the behavior of the radiative decay rate as a function of the plasmon wavelength leads to a transition from an exponential decay of the collective excitation for short distances to an algebraic decay for large distances. Importantly, we show that the exponential decay is of a purely nonradiative origin. Our transparent model enables us to provide analytical expressions for the polarization-dependent plasmon excitation profile along the chain and for the associated propagation length. Our theoretical analysis constitutes an important step in the quest for the optimal conditions for plasmonic propagation in nanoparticle chains.
Collective plasmonic modes in two-dimensional periodic arrays of metal nanoparticles
Physical Review B, 2008
We investigate the collective plasmonic modes of metal nanoparticles in periodic two-dimensional (2D) arrays within a point-dipole description. The dynamic dispersion relations of the 2D arrays are obtained through a method which gives an effective polarizability describing the collective response of a system. Both the dispersion relations and mode qualities are simultaneously related to the imaginary part of the effective polarizability, which has contributions from the single-particle response as well as the interparticle coupling. The transverse long-range dipolar interaction is dominated by a wave term together with a purely geometrical constant representing the static geometrical contribution to resonant frequencies. As concrete examples, we considered small Ag spheres arranged in a square lattice. We find that inside the light cone, the transverse quasimode has a reasonably high mode quality, while the two in-plane modes show significant radiation damping. Near the light line, we observe strong coupling with free photons for the bands of the transverse mode and the transverse in-plane mode, and the longitudinal in-plane mode exhibits a negative group velocity inside the light cone. Vanishing group velocities in the light cone for all the quasimodes are found to be intrinsic properties of the 2D metal nanosphere dense arrays.