Electromagnetic field localization in nanoantennas is one of the leitmotivs that drives the development of plasmonics. The near-fields in these plasmonic nanoantennas are commonly addressed ...theoretically within classical frameworks that neglect atomic-scale features. This approach is often appropriate since the irregularities produced at the atomic scale are typically hidden in far-field optical spectroscopies. However, a variety of physical and chemical processes rely on the fine distribution of the local fields at this ultraconfined scale. We use time-dependent density functional theory and perform atomistic quantum mechanical calculations of the optical response of plasmonic nanoparticles, and their dimers, characterized by the presence of crystallographic planes, facets, vertices, and steps. Using sodium clusters as an example, we show that the atomistic details of the nanoparticles morphologies determine the presence of subnanometric near-field hot spots that are further enhanced by the action of the underlying nanometric plasmonic fields. This situation is analogue to a self-similar nanoantenna cascade effect, scaled down to atomic dimensions, and it provides new insights into the limits of field enhancement and confinement, with important implications in the optical resolution of field-enhanced spectroscopies and microscopies.
Rigid Body Dynamics Borisov, Alexey; Mamaev, Ivan S; Higher Education Press Ltd. Comp., Higher Education
2018, 2018-12-03, Letnik:
52
eBook
This book provides an up-to-date overview of results in rigid body dynamics, including material concerned with the analysis of nonintegrability and chaotic behavior in various related problems. The ...wealth of topics covered makes it a practical reference for researchers and graduate students in mathematics, physics and mechanics. Contents Rigid Body Equations of Motion and Their Integration The Euler - Poisson Equations and Their Generalizations The Kirchhoff Equations and Related Problems of Rigid Body Dynamics Linear Integrals and Reduction Generalizations of Integrability Cases. Explicit Integration Periodic Solutions, Nonintegrability, and Transition to Chaos Appendix A : Derivation of the Kirchhoff, Poincaré - Zhukovskii, and Four-Dimensional Top Equations Appendix B: The Lie Algebra e(4) and Its Orbits Appendix C: Quaternion Equations and L-A Pair for the Generalized Goryachev - Chaplygin Top Appendix D: The Hess Case and Quantization of the Rotation Number Appendix E: Ferromagnetic Dynamics in a Magnetic Field Appendix F: The Landau - Lifshitz Equation, Discrete Systems, and the Neumann Problem Appendix G: Dynamics of Tops and Material Points on Spheres and Ellipsoids Appendix H: On the Motion of a Heavy Rigid Body in an Ideal Fluid with Circulation Appendix I: The Hamiltonian Dynamics of Self-gravitating Fluid and Gas Ellipsoids
A fully quantum mechanical investigation using time-dependent density functional theory reveals that the field enhancement in a coupled nanoparticle dimer can be strongly affected by nonlinear ...effects. We show that both classical as well as linear quantum mechanical descriptions of the system fail even for moderate incident light intensities. An interparticle current resulting from the strong field photoemission tends to neutralize the plasmon-induced surface charge densities on the opposite sides of the nanoparticle junction. Thus, the coupling between the two nanoparticles and the field enhancement is reduced as compared to linear theory. A substantial nonlinear effect is revealed already at incident powers of 109 W/cm2 for interparticle separation distances as large as 1 nm and down to the touching limit.
We present the optical response of two interacting metallic nanowires calculated for separation distances down to angstrom range. State-of-the-art local and nonlocal approaches are compared with full ...quantum time-dependent density functional theory calculations that give an exact account of nonlocal and tunneling effects. We find that the quantum results are equivalent to those from classical approaches when the nanoparticle separation is defined as the separation between centroids of the screening charges. This establishes a universal plasmon ruler for subnanometric distances. Such a ruler not only impacts the basis of many applications of plasmonics, but also provides a robust rule for subnanometric metrology.
The methods of classical differential geometry are used to integrate the two-dimensional Heisenberg model. After the hodograph transformation, the model equations are written in terms of the metric ...tensor associated with a curvilinear coordinate system and its derivatives. It is shown that their general solution describes all previously known exact solutions except a flat vortex. A new type of vortex structure, a “vortex strip,” is predicted and analyzed in two-dimensional ferromagnets. Its typical properties are the finite dimensions of the domain of definition, the finiteness of the total energy, and the absence of a vortex core in the presence of a vortex structure.
The optical properties of a nanoparticle dimer bridged by a conductive junction depend strongly on the junction conductivity. As the conductivity increases, the bonding dimer plasmon blueshifts and ...broadens. For large conductance, a low energy charge transfer plasmon also appears in the spectra with a line width that decreases with increasing conductance. A simple physical model for the understanding of the spectral feature is presented. Our finding of a strong influence of junction conductivity on the optical spectrum suggests that plasmonic cavities might serve as probes of molecular conductance at elevated frequencies not accessible through electrical measurements.
With examples of two parallel dielectric gratings and two arrays of thin parallel dielectric cylinders, it is shown that the interaction between trapped electromagnetic modes can lead to scattering ...resonances with practically zero width. Such resonances are the bound states in the radiation continuum first discovered in quantum systems by von Neumann and Wigner. Potential applications of such photonic systems include: large amplification of electromagnetic fields within photonic structures and, hence, enhancement of nonlinear phenomena, biosensing, as well as perfect filters and waveguides for a particular frequency, and impurity detection.
The main theoretical and experimental results of the study of magnetic skyrmions in films of isotropic chiral magnets are considered. A significant part of the paper presents new results that were ...not included in previous monographs and reviews. Skyrmions are formations characterized by a quantized topological number. They attract considerable attention of researchers due to their dynamics in external fields, which has promising features in terms of applications in spintronics. Special attention is given to the structure and interaction of 3D skyrmions, and a new magnetic structure - the chiral bobber - is considered.
Ne atoms with energies of ≤3 keV are diffracted under grazing angles of incidence from a LiF(001) surface. For a small momentum component of the incident beam perpendicular to the surface, we observe ...an increase in the elastic rainbow angle together with a broadening of the inelastic scattering profile. We interpret these two effects as the refraction of the atomic wave in the attractive part of the surface potential. We use a fast, rigorous dynamical diffraction calculation to find a projectile-surface potential model that enables a quantitative reproduction of the experimental data for ≤10 diffraction orders. This allows us to extract an attractive potential well depth of 10.4 meV. Our results set a benchmark for more refined surface potential models that include the weak van der Waals region, a long-standing challenge in the study of atom-surface interactions.
All published experimental data on Rh solubility in silicate melts were combined to derive an equation relating Rh solubility to temperature, oxygen fugacity, and a melt composition. It is ...demonstrated that Rh is dissolved in a melt dominantly as Rh
2+
in the entire experimental
f
O
2
range, from pure oxygen to QFM + 2 (QFM is the quartz–magnetite–fayalite buffer). The temperature dependence of Rh solubility is anomalous. Similar to the solubilities of other noble metals, Rh solubility at a constant
f
O
2
increases with increasing temperature. The Rh metal/silicate partition coefficient was calculated (
≈ 3.5 × 10
7
) for the expected conditions of Earth differentiation into a core and mantle. It is demonstrated that the late chondritic veneer model is able to best explain high Rh contents in upper mantle rocks. The suggested equation makes it possible to discard experimental glasses contaminated with metallic Rh micronuggets and thus to get rid of at least the most gross errors in the determination of Rh partition coefficients between rock-forming minerals and melt.
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