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.     

Giant strengthening of superconducting pairing in metallic nanoclusters

The presence of shell structure and the accompanying high level degeneracy leads to a strengthening of the pairing interaction in some metallic nanoclusters. It is predicted that for specific systems one can expect a large increase in the values of the critical temperature and other parameters.     

Molecular dynamics simulation of manipulation of metallic nanoclusters on stepped surfaces

Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on stepped surfaces. Five surface forms are considered in the simulations. The system parts are made of pure transition metals and Sutton-Chen many-body potential is used as interatomic potential. The conditions which are subjected to change in the tests include: materials used for particles and substrate, and surface step conditions. In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Simulation results show the effect of the aforementioned working conditions on the particle behavior as well as changes in the pushing forces. Obtaining this sort of knowledge is highly beneficial for further experiments in order to be able to plan the conditions and routines which guarantee better success in the manipulation process.     

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.     

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.     

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.     

Computational study on tuning the 2D self assembly of metallic nanoclusters

We discuss the size selection of metallic 2D clusters in cases where the growth proceeds on flat or wedged surfaces. The growth of nanoclusters is modelled using reaction kinetic model rate equations, where the kinetics are described by size dependent attachment and detachment rates, and the energetics are described through the free energy difference of the clusters. The model describes how the optimum stationary size and small size dispersion are reached, and what are the properties of the stationary size distribution. In addition to the geometrical factors, it is shown that the deposition flux can also be used to tune the size distribution towards the desired property.     

Structure of metallic nanowires and nanoclusters formed in superfluid helium

It is shown that metallic nanowires (5–8 nm in diameter) that form during laser ablation of Ni, Pb, In, and Sn targets embedded in HeII contain extended single-crystal segments, while spherical clusters (about 2 μm in diameter) that form under these conditions have a regular shape and an atomically smooth surface. Such structures are explained by melting of metal ablation products under their coalescence in HeII. The short-term action of a low-intensity beam of electrons with an energy of 200 keV initiates the explosion in metallic spheres preserved in the vacuum chamber of a transmission electron microscope, which is accompanied with the formation of thousands of clusters with a diameter of a few nanometers. This effect is due to metastability of internal mechanical stresses produced upon sharp cooling of molten spheres by liquid helium. A mechanism of condensation of atoms and nanoparticles in quantized vortices of superfluid helium is proposed.     

Logic gates scheme based on Coulomb blockade in metallic nanoclusters with organic ligands

We propose a logic gates scheme based on the electron transfer through metallic nanoclusters linked to organic ligands and discuss theoretically the characteristics needed for practical implementation. As a proof-of-the-concept, we demonstrate the OR, AND and NOT gates and study the performance in terms of temperature, applied voltage, and noise.     

Strong pair correlation in small metallic nanoclusters: the energy spectrum

The electronic shell structure in small metallic nanoclusters leads to high level degeneracy, which is strongly beneficial for the appearance of pair correlation. This results in a high value of T_c as well as in the appearance of a superconducting gap which causes a strong modification of the energy spectrum. The electronic energy spectrum becomes strongly temperature dependent. Consequently, specific experiments to demonstrate the presence of pair correlation can be proposed.     

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.     

Sound generation by spheroidal metallic nanoclusters embedded in transparent matrix under the action of laser pulses

The theory of the photo-acoustical effect caused by a laser action on metal nanoclusters embedded in a dielectric matrix is build. The energy absorbed by clusters propagates through the dielectric matrix and generates the sound waves in it via the thermodeformation mechanism. The formulae for an acoustical signal are derived, and the high sensitivity of the sound wave amplitude to the shape of metal clusters, as well to such parameters of a laser irradiation as the frequency, polarization, and intensity, is revealed. The behavior of the sound vibrations amplitude in a region of the surface plasmons absorption is studied in detail. It is found that this amplitude at light absorption by a discrete metal film (a system of clusters in the matrix) can exceed the corresponding amplitude for the absorption by a continuous metal film in the region of plasmon resonances by several orders of magnitude.     

海啸、地震海啸与海啸地震

简要地介绍了海啸与地震海啸的成因、特点,分析了影响地震海啸的重要因素,阐述了海啸预警的物理基础.以2004年12月26日苏门答腊-安达曼MW9.0特大地震及其激发的印度洋特大海啸为例,说明除了地震的大小、地震机制、震源深度以外,震源破裂过程也是影响地震激发海啸的重要因素.通过对苏门答腊-安达曼特大地震及2005年3月28日苏门答腊北部特大地震进行分析对比,探讨了海啸地震的特征,阐明了进一步深入研究海啸地震的特征及其激发海啸的机制对于预防和减轻海啸灾害的重要意义.     

纳米铜团簇扩散性质研究

本文通过分子动力学模拟研究了纳米铜团簇的自扩散性质,结果表明Nc8949铜团簇自扩散系数随温度的升高而增大,在温度为1000 K时纳米铜团簇的扩散系数随团簇半径的倒数基本呈线性增加.同时指出在常温下团簇几乎无扩散行为,而某些文献中关于常温下晶粒扩散分子动力学模拟结果是模拟体系宏观转动造成的虚假现象.?     

基于表面等离激元的偏振态控制光开关

利用四个Au纳米棒组成的类矩形纳米棒四聚体结构设计了一种基于偏振态控制的光开关,并采用有限元法研究了该结构对入射光偏振态的响应特性.研究发现,该结构的透射光谱对入射光的偏振方向具有很强的依赖性,当入射光的偏振角度变化π/2时,其特征峰的开关比分别能达到27.81dB和21.65dB.分析表明,该结构的开关效应主要由不同偏振态下所导致的水平双纳米棒和竖直双纳米棒之间的近场耦合强度不同而实现,该结构透射系数与偏振角度的关系服从Malus law.此外,通过改变类矩形纳米棒阵列结构参数,研究了结构参数对其光开关响应特性的影响.在此基础上,通过改变阵列的周期参数,研究了入射光水平偏振和垂直偏振下周期参数对单元结构透射光谱的影响.该研究结果能够为可调谐双波长偏振光开关的设计提供理论依据.     

Interface and contact structures for nanoelectronic devices using assemblies of metallic nanoclusters,conjugated organic molecules and chemically stable semiconductor layers

Self-assembly (‘building’) approaches can provide well-controlled structures and assemblies at the nanometer scale, but typically do not provide the specific structures or functionalities required for robust nanoelectronic circuits. One approach to realize high-density nanoelectronic circuits is to combine self-assembly techniques with more conventional semiconductor device and circuit approaches (‘chiseling`) in order to provide suitable functionality and arbitrary circuit functions. An interesting challenge is to find approaches where these techniques can be combined to realize suitable device structures. This paper describes recent work which combines self-assembly techniques involving metal nanoclusters and conjugated organic molecules with semiconductor interface and device structures to form structures of interest for nanoelectronics. One key requirement for this approach is the availability of a chemically stable semiconductor surface layer, which can provide a low-resistance interface between the metallic nanostructure and the semiconductor device layers following room-temperature, ex situ processing. As an illustration of the structures which can be realized, we describe a nanometer-scale ohmic contact to n-type GaAs which utilizes low-temperature-grown GaAs as the chemically stable interface layer. Contact structures have been realized using both isolated (sparse) clusters and using close-packed arrays of clusters on the surface. The low-resistance contacts between the nanoclusters and the semiconductor device layers indicates that relatively low surface barriers and high doping densities have been achieved in these ex situ structures. The general conduction model for this contact structure is described in terms of the interface electrical properties and the contributions from the various components are discussed.     

Cooperative superfluorescence in nanoclusters

The features of superfluorescence (SF) in nanoclusters, which consist of a few neighboring particles interacting with each other by exchange or/and electrostatic forces, are investigated theoretically. It is shown that there are two types of cooperatively SF depending on the ratio between the linear size of a nanocluster and the cooperative interaction range. Experiments on cooperative luminescence in Ytterbium-doped silica fibers are analyzed. It is shown that the intensity of cooperative SF in such a system should be proportional to the fourth degree of Ytterbium concentration.