Plasmon excitations in homogeneous neutron-star matter

We study the possible collective plasma modes which can affect neutron-star thermodynamics and different elementary processes in the baryonic density range between nuclear saturation ρ ₀ and 3ρ ₀. In this region, the expected constituents of neutron-star matter are mainly neutrons, protons, electrons, and muons (npeμ matter), under the constraint of beta equilibrium. The elementary plasma excitations of the peμ three-fluid medium are studied in the RPA framework. We emphasize the relevance of the Coulomb interaction among the three species, in particular, the interplay of the electron and muon screening in suppressing the possible proton plasma mode, which is converted into a sound-like mode. The Coulomb interaction alone is able to produce a variety of excitation branches and the full spectral function shows a rich structure at different energy. The genuine plasmon mode is pushed at high energy and it contains mainly an electron component with a substantial muon component, which increases with density. The plasmon is undamped for not too large momentum and is expected to be hardly affected by the nuclear interaction. All the other branches, which fall below the plasmon, are damped or over-damped. The text was submitted by the authors in English.     

Plasmon hybridization in metallic nanotubes

We study theoretical formalism of the plasmon hybridization in a metallic nanotube and find an explicit form of the dispersion relation for surface plasmons, in terms of interaction between the bare plasmon modes of the individual surfaces of the nanotubes. In the special case when the longitudinal wave vector is zero (q=0), the plasmon hybridization of a nanotube has a behavior similar to the spherical nanoshell.     

Plasmon and magneto-plasmon excitations in double heterostructures

The plasmon and magneto-plasmon spectra are analyzed for an electron system which consists of two parallel two-dimensional electron layers which are separated from each other by a certain distance2d. Our approach allows to consider these electron liquids to be on different levelsE ₁ andE ₂ and to regard an arbitrary tunneling probabilityt between them. The Coulomb interaction is treated by means of a random-phase approximation. The resulting modes reflect typical features of the system: there are different plasmon branches connected with either the total or the reduced charge density and a further collective mode consisting of electron transitions from one to another electron layer. The influence of a static external magnetic fieldB applied perpendicularly to the electron layers leads to characteristic combinations of the plasmon modes (forB=0) with the cyclotron frequency _c .     

Plasmon hybridization in metallic nanotubes with a nonconcentric core

We develop a theory of plasmon excitations in a metallic nanotube with a nonconcentric core using the plasmon hybridization method. We apply the two-center cylindrical coordinate system for mathematical convenience and find an explicit form of the dispersion relation for surface plasmons, in terms of interaction between the bare plasmon modes of the individual surfaces of the nanotubes. We present numerical result displaying the effect of the offset distant d of the inner core from the nanotube center, when there is no angular momentum transfer, i.e., m=0. For large offsets, the plasmon shifts is strong, but weak for small offset.     

Plasmon tsunamis on metallic nanoclusters

A model is constructed to describe inelastic scattering events accompanying electron capture by a highly charged ion flying by a metallic nanosphere. The electronic energy liberated by an electron leaving the Fermi level of the metal and dropping into a deep Rydberg state of the ion is used to increase the ion kinetic energy and, simultaneously, to excite multiple surface plasmons around the positively charged hole left behind on the metal sphere. This tsunami-like phenomenon manifests itself as periodic oscillations in the kinetic energy gain spectrum of the ion. The theory developed here extends our previous treatment (Lucas et al 2011 New J. Phys. 13 013034) of the Ar(q+)/C(60) charge exchange system. We provide an analysis of how the individual multipolar surface plasmons of the metallic sphere contribute to the formation of the oscillatory gain spectrum. Gain spectra showing characteristic, tsunami-like oscillations are simulated for Ar(15+) ions capturing one electron in distant collisions with Al and Na nanoclusters.     

Coulomb excitations of a nuclear slab in relativistic mean-field theory

Time-dependent relativistic mean-field theory is used to describe the dynamic behaviour of a nuclear slab excited at time zero by a rapid Coulomb push. At small incident energies of the projectile, we observe oscillations of small amplitude with isovector character. With increasing excitation energy, the motion becomes increasingly anharmonic, and parts of the nuclear material are ejected. At the highest energies, we find a rapid dissociation between the proton and neutron part of the slab. It turns out that the character of the oscillations is strongly influenced by the strength of the ρ-meson coupling. For vanishing coupling, we observe two modes corresponding in nature to the Goldhaber-Teller mode and the Steinwedel-Jensen mode of the giant dipole resonance in realistic nuclei. At larger ρ-meson coupling, the Goldhaber-Teller mode is more and more suppressed, and one is left with one strongly damped mode of the Steinwedel-Jensen type.     

Long-range surface polaritons in a supported thin metallic slab

It is shown that a thin metallic slab supported by a thick transparent slab may guide infrared surface polaritons (SP) with propagation lengths larger than those of SP in a semi-infinite metals. These long-range SP are “virtual” in the sense that their electromagnetic field is oscillatory across the supporting slab.     

Modulation instability of electromagnetic excitations for a Josephson unction in a finite-thickness slab

The modulation instability of finite-amplitude uniform plane waves oscillating with a Josephson frequency and experiencing a nonlinear frequency shift in a finite-thickness slab is studied in terms of the nonlocal electrodynamics of Josephson junction. A dispersion relation for the growth rate of small amplitude perturbation is derived. The domains of modulation instability for these waves are found. Modulation instability of the waves is shown to arise when the wavevectors of long-wave amplitude perturbations fall into the finite range 0 < Q < Q _B (A, D, L). In the range Q ≥ Q _B (A, D, L), the waves are stable.     

Plasmon electro-optic effect in a subwavelength metallic nanograting with a nematic liquid crystal

The electro-optic effect in hybrid structures based on subwavelength metallic nanogratings in contact with a layer of a nematic liquid crystal has been experimentally studied. Metallic gratings are fabricated in the form of interdigitated electrodes, which makes it possible to use them not only as optical elements but also for the production of an electric field in a thin surface region of the layer of the liquid crystal. It has been shown that, owing to the electric-field-induced reorientation of molecules of the liquid crystal near the surface of the grating, it is possible to significantly control the spectral features of the transmission of light, which are caused by the excitation of surface plasmons. The electro-optic effect is superfast for liquid crystal devices because a change in the optical properties of the system requires the reorientation of molecules only in a very thin surface layer of the liquid crystal.     

Evolution of spin-wave excitations in ferromagnetic metallic manganites

Neutron scattering results are presented for spin-wave excitations of three ferromagnetic metallic A1-xA'xMnO3 manganites (where A and A' are rare- and alkaline-earth-metal ions), which when combined with previous work elucidate the systematics of the interactions as a function of carrier concentration x, on-site disorder, and strength of the lattice distortion. The long-wavelength spin dynamics show only a very weak dependence across the series. The ratio of fourth to first neighbor exchange (J4/J1) that controls the zone boundary magnon softening changes systematically with x, but does not depend on the other parameters. None of the prevailing models can account for these behaviors.     

Plasmon dispersion in metallic lithium–ammonia solutions

Inelastic X-ray scattering spectra of lithium (Li)–ammonia solutions with concentrations of 9, 13, and 17 mol.% metal have been measured with 0.05- and 0.38-eV resolution for momentum transfer between 0.18 and 0.56 Å⁻¹. The peak growing with Li-concentration was found around 2 eV, and was assigned to the plasmon of delocalized Li-2s electrons. The plasmon shows a positive dispersion, indicating that exchange–correlation effects in actual nearly free electrons are considerably smaller than expected.     

Phonon scattering by electrons and low energy excitations in a metallic glass

Measurements of the thermal conductivity of a superconducting metallic glass Zr₇₀Cu₃₀ in zero field and in a magnetic field exceeding the upper critical field allow a quantitative determination of the strength of the phonon-electron scattering for the first time in amorphous metals. The temperature dependence of the residual phonon scattering by localized low energy excitations is similar to that found in insulating glasses.     

Controlling the focusing properties of a triangular-lattice metallic photonic-crystal slab：

This paper studies the focusing properties of a two-dimensional photonic crystal (PC) slab consisting of a triangular lattice of metallic cylinders immersed in a dielectric background. Through the analysis of the equifrequency-surface contours and the field patterns of a point source placed in the vicinity of the PC slab, it finds that both the image distance and image quality can be controlled by simply adjusting the refractive index of the background material.     

Light collimation and focusing by a thin flat metallic slab

We present experimental and theoretical work showing that a flat metallic slab can collimate and focus light impinging on the slab from a point source. The effect is optimized when the radiation is around the bulk, not at the surface, plasma frequency. Also, the smaller the imaginary part of the permittivity is, the better the collimation. Experiments for Ag in the visible as well as calculations are presented. We also discuss the interesting case of Al, whose imaginary part of permittivity is very small at the plasma frequency in UV radiation. Generalization to other materials and radiations are also discussed.     

Line width of crystal-field excitations in metallic rare-earth systems

A theory is developed for the line width of crystal-field excitations in metallic rare-earth systems were the damping is due to conduction electron-hole excitations. First the single ion or dilute alloy case is studied. As an example the theory is applied to Ce in LaAl₂ and compared with recent experiments. Then the case of a regular lattice of rare-earth ions is considered. The theory is applied to the ₁ – ₄ system. Special attention is paid to the behaviour of the central peak near an induced-moment phase transition. It is shown that the dynamics of the conduction electrons leads to observable effects in the centralpeak intensity and can not be neglected as it is usually done. The theoretical predictions are in agreement with recent experimental findings on Pr₃Tl.     

Plasmon spectroscopy of metallic nanoparticles above flat dielectric substrates

We numerically analyze the spectral properties of localized plasmon resonances in metal nanoparticles when these are above a dielectric substrate. This analysis is performed as a function of the various parameters involved in the problem (relative optical properties, particle-substrate separation, angle of incidence, etc.). It can be shown that from the spectral behavior of the resonance in the far field, information about particle near-field interactions can be obtained.