Low-frequency plasmons in coupled electronic microstructures

The plasmon spectrum and the absorption of an electromagnetic wave in an electronic two-dimensional plasma with strongly modulated density are studied. The appearance of additional plasmon modes in a system of electronic wires and islands with weak current coupling is described in a model of an electronic system covered with metallic gates. Such plasmon modes appear in the low-frequency region of the spectrum, as compared with the conventional plasma oscillations, and have recently been observed experimentally in paired wires. Fiz. Tverd. Tela (St. Petersburg) 40, 542–545 (March 1998)     

Effects of saturation on optical bistability with coupled surface plasmons

We present exact numerical results for a symmetric layered medium (prism/Ag film/nonlinear dielectric/Ag film/prism) where the middle dielectric slab is assumed to have a saturation-type nonlinearity. We show bistable behaviour in the power dependence of the reflectivity ofp-polarized light under the condition when coupled surface modes are excited in the structure. Moreover, we study the effect of saturation on the bistable behaviour to show that multivalued character is inhibited by saturation effects. The field distributions corresponding to the minimum reflectivity states of the nonlinear structure are also presented.     

Propagating anti-symmetrically coupled plasmons generation by electron beams

Propagating anti-symmetrically coupled plasmons that usually cannot be excited with incident light and radiate to far field can be efficiently generated by electron beams. An electron beam is proposed as a practical propagating anti-symmetrically coupled plasmon source due to that it couples differently to the surface plasmons than free radiation. Specifically, whispering-gallery anti-symmetrically coupled plasmons with the character of symmetrical coupled dipoles are excited by an electron beam in a nested ringlike waveguide, which is consistent with the dispersion of electron excited plasmons in an infinite-long nanowire pair.     

Transverse spin effects in diffractive hadron leptoproduction

We consider double spin asymmetries for longitudinally polarized leptons and transversely polarized protons in diffractive vector meson and production at high energies within the two-gluon model. The connection of the two-gluon approach with skewed gluon distributions is discussed. The asymmetry predicted for meson production is quite small. The asymmetry for production contains two independent terms which are large and can be used to obtain information on the polarized skewed gluon distributions in the proton. Received: 19 February 2002 / Revised version: 19 March 2002 / Published online: 22 May 2002     

Transverse single spin asymmetry measurements at STAR

Transverse single spin asymmetries A _N are expected to be sensitive to par-ton polarization and orbital angular momentum contributions to the nucleon spin. Significantly large A _N has been observed in different collision systems such as semi-inclusive deep inelastic scattering (SIDIS) and polarized proton-proton (pp) collisions, indicating a dominant contribution of partonic interactions in the non-perturbative regime. Therefore it’s critical to measure A _N in various channels of polarized pp collisions in order to complement SIDIS data and to constrain theoretical models. We report STAR asymmetry measurements on mid-rapidity hadron-jet and di-hadron correlations at √s = 200 GeV and forward rapidity inclusive hadron production at √s = 500 GeV polarized pp collisions.     

Cavity QED with magnetically coupled collective spin states

We report strong coupling between an ensemble of nitrogen-vacancy center electron spins in diamond and a superconducting microwave coplanar waveguide resonator. The characteristic scaling of the collective coupling strength with the square root of the number of emitters is observed directly. Additionally, we measure hyperfine coupling to (13)C nuclear spins, which is a first step towards a nuclear ensemble quantum memory. Using the dispersive shift of the cavity resonance frequency, we measure the relaxation time of the NV center at millikelvin temperatures in a nondestructive way.     

Transverse magnetization transfer under planar mixing conditions in spin systems consisting of three coupled spins 1/2

Polarization transfer under planar mixing conditions is a widely used tool in modern NMR-experiments. In the case of two coupled spins 1/2 or a chain of three or more spins 1/2 with only nearest neighbor couplings, it is only possible to transfer a single magnetization component (longitudinal magnetization in the principle axis system of the planar coupling tensors). However, if all couplings in a three-spin system are non-zero, it turns out that all magnetization components can be efficiently transferred even under strictly planar mixing conditions. In this article a detailed theoretical analysis is presented based on analytical transverse coherence transfer functions and on the underlying commutator algebra. In addition, transverse magnetization transfer is demonstrated experimentally. The results show that in highly coupled spin systems, as for example in the case of partially aligned samples with many residual dipolar couplings, special care has to be taken to avoid phase distortions if planar mixing steps are used.     

Numerical simulations on longitudinal surface plasmons of coupled gold nanorods

We analyze numerically the localized surface plasmon resonance (LSPR) frequencies of coupled metal nanorods using discrete dipole approximation (DDA) and finite element method (FEM). The two configurations of identical nanorods are considered: end-to-end and side-by-side. Dependence of LSPR frequencies on the interparticle distance is determined by DDA. The latter for the case of large separations agrees with the result of approximate analytical method developed earlier for single metal nanorods. Distributions of electric near-fields of nanorods as well as enhancement factors at hot spots for both configurations are calculated by FEM.     

Transverse spin relaxation of spin carriers diffusing in spatially periodic magnetic fields

An exact solution of the Bloch–Torrey equation that covers the entire range of relative diffusivities D between the spin carriers and the magnetic structure (due to, e.g., spin‐density waves) is given for the transverse relaxation of an initally uniformly polarized spin system under the influence of a magnetic field varying sinusoidally in space. Explicit closed‐form results for the short‐time relaxation are obtained making use of Laplace transforms, the three‐term recurrence relations associated with Mathieu’s equation, and novel sum rules. At intermediate diffusivities the transverse polarization exhibits a novel long‐time behaviour as a function of D. This revised version was published online in August 2006 with corrections to the Cover Date.     

Transverse spin dynamics of a spin-polarized Fermi liquid

A microscopic derivation of the equations of transverse spin dynamics of a spin-polarized Fermi liquid at zero temperature is given in the leading-order approximation in the frequencies and wave vectors characterizing the spin motion. The equations are applicable for arbitrary degree of polarization and arbitrary deviations of the spin direction from the equilibrium orientation. The solutions describing a coherently precessing two-domain structure and spin waves are examined. In contrast to the assertion discussed in the literature that spin waves are damped at zero temperature, spin waves are found to be undamped in the long-wavelength limit. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 717–721 (10 May 1997)     

Transverse spin freezing in Fe92.5Hf7.5

Amorphous Fe_92.5Hf_7.5 has been studied by Mössbauer spectroscopy and magnetization measurements. Transverse spin freezing has been observed at 47 ± 8 K, and the results are compared with those for amorphous iron-rich Fe-Zr alloys in which transverse spin freezing is also observed.     

Transverse spin structure of hadrons from lattice QCD

This paper presents recent lattice QCD calculations of transverse spin densities of quarks in hadrons.² Based on our simulation results for the tensor generalized form factors, we find substantial correlations between spin and coordinate degrees of freedom in the nucleon and the pion. They lead to strongly distorted transverse spin densities of quarks in the nucleon and a surprisingly non-trivial transverse spin structure of the pion. Following recent arguments by Burkardt [M. Burkardt, Phys. Rev. D 72 (2005) 094020], our results imply that the Boer-Mulders function , describing correlations of the transverse spin and intrinsic transverse momentum of quarks, is large and negative for up-quarks in the proton and the π⁺. This supports the recent hypothesis that all Boer-Mulders functions are alike [arXiv:0705.1573], and also provides additional motivation for future studies of azimuthal asymmetries in πp Drell-Yan production at, e.g., COMPASS.     

Transverse spin and momentum correlations in quantum chromodynamics

The naive time reversal odd (‘T-odd’) parton distribution and fragmentation functions are explored. We use the spectator model framework to study flavour dependence of the Boer-Mulders (h ₁^⊥ ) and Sivers (f _1T^⊥) functions as well as the ‘T-even’ but chiral odd function h _1L^⊥. These transverse momentum-dependent parton distribution functions are of significance for the analysis of azimuthal asymmetries in semi-inclusive deep inelastic scattering, as well as for the overall physical understanding of the distribution of transversely polarized quarks in unpolarized hadrons. In this context we also consider the Collins mechanism and the fragmentation function H ₁^⊥. As a by-product of this analysis we calculate the leading twist unpolarized cos(2ϕ) asymmetry, and sin(2ϕ) single spin asymmetry for a longitudinally polarized target in semi-inclusive deep inelastic scattering.      

Particle plasmons resonant characteristics in arrays of strongly coupled gold nanoparticles

Using the finite difference time domain (FDTD) method, we investigated the optical properties of a periodic array of strongly coupled gold nanoparticles (MNPs). We show the two kinds properties of transmission spectra with both different interparticle spaces and different radii of the particles. It is found that some distinct extra resonant peaks appear in the forbidden band gap and the resonant frequency depends strongly on the space between the particles and the radius of the particles. Based on the localized nature of the field distribution, we also show clearly the presence of local plasmons resonant modes that originate from quadrupole plasmon polaritons.     

Back focal plane imaging of Tamm plasmons and their coupled emission

The unique optical properties of Tamm plasmons (TPs) – such as flexible wavevector matching conditions including inplane wavevector within the light line, and existing both S‐ and P‐polarized TPs − facilitate them for direct optical excitation. The Tamm plasmon‐coupled emission (TPCE) from a combined photonic–plasmonic structure sustaining both surface plasmons (SPs) and TPs is described in this paper. The sensitivity of TPCE to the emission wavelength and polarization is examined with back focal plane imaging and verified with the numerical calculations. The results reveal that the excited probe can couple with both TPs and SPs, resulting in surface plasmon‐coupled emission (SPCE) and TPCE, respectively. The TPCE angle is strongly dependent on the wavelength allowing for spectral resolution using different observation angles. These Tamm structures provide a new tool to control the optical emission from dye molecules and have many potential applications in fluorescence‐based sensing and imaging.