Search results for "Localized"
showing 10 items of 297 documents
Determinant role of the edges in defining surface plasmon propagation in stripe waveguides and tapered concentrators
2012
International audience; In this paper, we experimentally show the effect of waveguide discontinuity on the propagation of the surface plasmon in metal stripes and tapered terminations. Dual-plane leakage microscopy and near-field microscopy were performed on Au stripes with varied widths to imag29e the surface plasmon intensity distribution in real and reciprocal spaces. We unambiguously demonstrate that edge diffraction is the limiting process determining the cutoff conditions of the surface plasmon mode. Finally, we determine the optimal tapered geometry leading to the highest transmission.
Property (w) and perturbations
2007
A bounded linear operator T ∈ L(X) defined on a Banach space X satisfies property (w), a variant of Weyl’s theorem, if the complement in the approximate point spectrum σa(T ) of the Weyl essential approximate spectrum σwa(T ) coincides with the set of all isolated points of the spectrum which are eigenvalues of finite multiplicity. In this note, we study the stability of property (w), for a bounded operator T acting on a Banach space, under perturbations by finite rank operators, by nilpotent operator and quasi-nilpotent operators commuting with T .
Electric Field Control of Spin-Dependent Dissipative Electron Transfer Dynamics in Mixed-Valence Molecules
2015
We demonstrate that the borderline class II/III magnetic MV dimers, which can be referred to as single molecule multiferroics, provide a unique possibility to achieve electric field control of the electron transfer (ET) dynamics. As an example, we consider a MV dimer d2-d1 in which an extra electron is delocalized over two spin-cores (s0 = 1/2), and the ET is spin-dependent due to the double exchange mechanism. It is assumed that the “extra” electron is coupled to the only intramolecular vibration, and a weak coupling to the dissipative subsystem (thermal bath) is taken into account. The vibronic energy levels and the wave functions of the isolated dimer (quantum part of the system) are num…
Interplay of spin-dependent delocalization and magnetic anisotropy in the ground and excited states of [Gd2@C78]− and [Gd2@C80]−
2017
The magnetic properties and electronic structure of the ground and excited states of two recently characterized endohedral metallo-fullerenes, [Gd2@C78]- (1) and [Gd2@C80]- (2), have been studied by theoretical methods. The systems can be considered as [Gd2]5+ dimers encapsulated in a fullerene cage with the fifteen unpaired electrons ferromagnetically coupled into an S = 15/2 high-spin configuration in the ground state. The microscopic mechanisms governing the Gd-Gd interactions leading to the ferromagnetic ground state are examined by a combination of density functional and ab initio calculations and the full energy spectrum of the ground and lowest excited states is constructed by means …
Surface Lattice Resonances in Self-Assembled Arrays of Monodisperse Ag Cuboctahedra
2019
Plasmonic metal nanoparticles arranged in periodic arrays can generate surface lattice plasmon resonances (SLRs) with high Q-factors. These collective resonances are interesting because the associated electromagnetic field is delocalized throughout the plane of the array, enabling applications such as biosensing and nanolasing. In most cases such periodic nanostructures are created via top-down nanofabrication processes. Here we describe a capillary-force-assisted particle assembly method (CAPA) to assemble monodisperse single-crystal colloidal Ag cuboctahedra into nearly defect-free >1 cm2 hexagonal lattices. These arrays are large enough to be measured with conventional ultraviolet-visibl…
Hydrogen-Bond Cooperative Effects in Small Cyclic Water Clusters as Revealed by the Interacting Quantum Atoms Approach
2013
The cooperative effects of hydrogen bonding in small water clus- ters (H2O)n (n = 3-6) have been studied by using the partition of the electronic energy in accordance with the interact- ing quantum atoms (IQA) approach. The IQA energy splitting is comple- mented by a topological analysis of the electron density (1(r)) compliant with the quantum theory of atoms-in-mole- cules (QTAIM) and the calculation of electrostatic interactions by using one- and two-electron integrals, thereby avoiding convergence issues inherent to a multipolar expansion. The results show that the cooperative effects of hy- drogen bonding in small water clusters arise from a compromise between: 1) the deformation energ…
A density functional investigation of thiolate-protected bimetal PdAu24(SR)18z clusters: doping the superatom complex
2009
Structure, electronic properties, optical absorption and charging properties of methylthiolate-protected bimetal PdAu(24)(SR)(18)(z) (R = Me) clusters with various charge states (-3or=zor= +3) are investigated by using density functional theory. The results are compared to properties of the well-understood singly anionic pure gold complex Au(25)(SR)(18)((-1)) [J. Akola, M. Walter, H. Häkkinen and H. Grönbeck, J. Am. Chem. Soc., 2008, 130, 3756]. The atomic structure of this all-gold complex can be written in a "divide-and-protect" way [H. Häkkinen, M. Walter and H. Grönbeck, J. Phys. Chem. B, 2006, 110, 9927] as Au(13)[Au(2)(SR)(3)](6)((-1)) where 6 v-shaped Au(2)(SR)(3) ligands protect the…
Location of holes in silicon-rich oxide as memory states
2002
The induced changes of the flatband voltage by the location of holes in a silicon-rich oxide (SRO) film sandwiched between two thin SiO 2 layers [used as gate dielectric in a metal-oxide-semiconductor (MOS) capacitor] can be used as the two states of a memory cell. The principle of operation is based on holes permanently trapped in the SRO layer and reversibly moved up and down, close to the metal and the semiconductor, in order to obtain the two logic states of the memory. The concept has been verified by suitable experiments on MOS structures. The device exhibits an excellent endurance behavior and, due to the low mobility of the holes at low field in the SRO layer, a much longer refresh …
Investigation on the microscopic structure of E' center in amorphous silicon dioxide by electron paramagnetic resonance spectroscopy
2006
The E′δ center is one of the most important paramagnetic point defects in amorphous silicon dioxide ( a-SiO 2) primarily for applications in the field of electronics. In fact, its appearance in the gate oxide of metal-oxide-semiconductor (MOS) structures seriously affects the proper work of many devices and, often, causes their definitive failure. In spite of its relevance, until now a definitive microscopic model of this point defect has not been established. In the present work we review our experimental investigation by electron paramagnetic resonance (EPR) on the E′δ center induced in γ-ray irradiated a-SiO 2. This study has driven us to the determination of the intensity ratio between…
Electron paramagnetic resonance investigation on the hyperfine structure of the center in amorphous silicon dioxide
2007
Abstract We report an experimental investigation by electron paramagnetic resonance (EPR) spectroscopy on the hyperfine structure of the E δ ′ center in γ-ray irradiated amorphous silicon dioxide materials. This study has driven us to the determination of the intensity ratio between the hyperfine doublet and the main resonance line of this point defect. This ratio was obtained for a variety of silica samples and compared with the analogous ratio obtained for the E γ ′ defect. The comparison definitively confirms that the electronic wave function involved in the E δ ′ center is actually delocalized over four nearly equivalent Si atoms.