Partial Wave Decomposition for Meson Exchange Currents in Few-Nucleon Systems

We develop an approach for calculating matrix elements of meson exchange currents between 3N basis states in (jJ)-coupling and a 3N bound state. The contribution generated by $\pi$- and $\rho$-exchange are included in the consideration. The matrix elements are expressed in terms of multiple integrals in the momentum space. We apply a technique of the partial wave decompositions and carry out some angular integrations in closed form. Different representations appropriate for numerical calculations are derived for the matrix elements of interest. The momentum dependences of the matrix elements are studied and benchmark results are presented. The approach developed is of interest for the investigations of deuteron- proton radiative capture and ^3He photo- and electrodisintegration when the interaction in the initial or final nuclear states is taken into account by solving the Faddeev equations.Comment: 32pages (14 figures

Subwavelength micropolarizer in a gold film for visible light

Engineering and Physical Sciences Research Council (EPSRC) (EP/L017008/1); European Research Council (337508); Russian Foundation for Basic Research (RFBR) (14-07-97039, 14-29-07133, 15-07-01174, 15-37-20723, 16-07-00990, 16-29-11698); Ministry of Education and Science of the Russian Federation (MK-9019.2016.2).We have designed and fabricated a 100 μm x 100 μm four-sector binary subwavelength reflecting polarization microconverter in a gold film. Using finite-difference time-domain-aided numerical simulations and experiments, the micropolarizer was shown to convert an incident linearly polarized Gaussian beam of wavelength 532 nm into an azimuthally polarized beam. Conditions for generating on-axis regions of nonzero intensity when using propagating optical vortices with different initial polarization were deduced. By putting a spiral phase plate into an azimuthally polarized beam, the intensity pattern was shown to change from diffraction rings to a central peak.PostprintPeer reviewe

Robust Multi-Partite Multi-Level Quantum Protocols

We present a tripartite three-level state that allows a secret sharing protocol among the three parties, or a quantum key distribution protocol between any two parties. The state used in this scheme contains entanglement even after one system is traced out. We show how to utilize this residual entanglement for quantum key distribution purposes, and propose a realization of the scheme using entanglement of orbital angular momentum states of photons.Comment: 9 pages, 2 figure

Local vibrations in real crystals with combined defects

The conditions of formation and the main characteristics of local vibrations due to the presence of light impurities Al, Mg, and Mn in the bulk and on the close-packed [111] surface of the fcc crystal lattice of silver are investigated. The influence of surface roughness is analyzed. Analytical approximations are obtained which describe the frequency and intensity of the local vibrations at the impurity atom and its nearest neighborhood to high accuracy. The proposed analytical approximations provide a practical way of determining the parameters of the defect structure and the interatomic interactions from the experimentally determined characteristics of the local vibrations

Spin structure of three-nucleon bound states

The spin-dependent momentum distributions (SDMDs) of nucleons and proton-deuteron clusters in polarized ³He and ³H nuclei are studied with wave functions (WFs) for realistic models of nuclear forces.Хвильові функції для реалістичних моделей ядерних сил використовуються для дослідження залежних від спина імпульсних розподілів нуклонів і нуклон-дейтронних кластерів у поляризованих ядрах ³He та ³H.Волновые функции для реалистических моделей ядерных сил используются для исследования зависящих от спина импульсных распределений нуклонов и нуклон-дейтронных кластеров в поляризованных ядрах ³He и ³H

Magnetization in short-period mesoscopic electron systems

We calculate the magnetization of the two-dimensional electron gas in a short-period lateral superlattice, with the Coulomb interaction included in Hartree and Hartree-Fock approximations. We compare the results for a finite, mesoscopic system modulated by a periodic potential, with the results for the infinite periodic system. In addition to the expected strong exchange effects, the size of the system, the type and the strength of the lateral modulation leave their fingerprints on the magnetization.Comment: RevTeX4, 10 pages with 14 included postscript figures To be published in PRB. Replaced to repair figure

Subwavelength grating-based spiral metalens for tight focusing of laser light

In this paper, we investigate a 16-sector spiral metalens fabricated on a thin film (130 nm) of amorphous silicon, consisting of a set of subwavelength binary diffractive gratings and with a numerical aperture that is close to unity. The metalens converts linearly polarized incident light into an azimuthally polarized optical vortex and focuses it at a distance approximately equal to the wavelength of the incident light, k ¼ 633 nm. Using a scanning near-field optical microscope, it is shown experimentally that the metalens forms an elliptical focal spot with diameters smaller than the diffraction limit: FWHMx ¼ 0.32k (60.03k) and FWHMy ¼ 0.51k (60.03k). The experimental results are close to those of a numerical simulation using the FDTD method, with FWHMx ¼ 0.37k and FWHMy ¼ 0.49k. The technological errors due to manufacturing were taken into account in the simulation. This is the smallest focal spot yet obtained with a metalens

Tight focusing of laser light using a chromium Fresnel zone plate

Funding: Russian Scientific Foundation (17-19-01186).Using near-field scanning microscopy, we demonstrate that a 15-µm zone plate fabricated in a 70-nm chromium film sputtered on a glass substrate and having a focal length and outermost zone's width equal to the incident wavelength λ = 532 nm, focuses a circularly polarized Gaussian beam into a circular subwavelength focal spot whose diameter at the full-width of half-maximum intensity is FWHM = 0.47λ. This value is in near-accurate agreement with the FDTD-aided numerical estimate of FWHM = 0.46λ. When focusing a Gaussian beam linearly polarized along the y-axis, an elliptic subwavelength focal spot is experimentally found to measure FWHMx = 0.42λ (estimated value FWHMx = 0.40λ) and FWHMy = 0.64λ. The subwavelength focal spots presented here are the tightest among all attained so far for homogeneously polarized beams by use of non-immersion amplitude zone plates.PostprintPeer reviewe