Search results for "CONDENSED MATTER"
showing 10 items of 13918 documents
Localized surface plasmon resonance in silver nanoparticles: Atomistic first-principles time-dependent density-functional theory calculations
2015
We observe using ab initio methods that localized surface plasmon resonances in icosahedral silver nanoparticles enter the asymptotic region already between diameters of 1 and 2 nm, converging close to the classical quasistatic limit around 3.4 eV. We base the observation on time-dependent density-functional theory simulations of the icosahedral silver clusters Ag$_{55}$ (1.06 nm), Ag$_{147}$ (1.60 nm), Ag$_{309}$ (2.14 nm), and Ag$_{561}$ (2.68 nm). The simulation method combines the adiabatic GLLB-SC exchange-correlation functional with real time propagation in an atomic orbital basis set using the projector-augmented wave method. The method has been implemented for the electron structure…
Time resolved emission at 1.3 μm of a single InAs quantum dot by using a tunable fibre Bragg grating
2013
Photoluminescence and time resolved photoluminescence from single metamorphic InAs/GaAs quantum dots (QDs) emitting at 1.3 mu m have been measured by means of a novel fibre-based characterization set-up. We demonstrate that the use of a wavelength tunable fibre Bragg grating filter increases the light collection efficiency by more than one order of magnitude as compared to a conventional grating monochromator. We identified single charged exciton and neutral biexciton transitions in the framework of a random population model. The QD recombination dynamics under pulsed excitation can be understood under the weak quantum confinement potential limit and the interaction between carriers at the …
Electronic polarizability of small metal spheres
1985
We present the results of calculations for the ground-state electron structure, static polarizability, and dynamic response of small metal (jellium) spheres in vacuum or embedded in a dielectric. Fully self-consistent time-dependent density-functional methods are used. In particular, the static and dynamic responses to an incident electric field (dipolar polarizability and photoabsorption) are obtained. The results show substantial deviations from either classical or approximate quantum-mechanical solutions, and provide reference data for simplified treatments. Peer reviewed
Ti Alloyed α-Ga2O3: Route towards Wide Band Gap Engineering
2020
The suitability of Ti as a band gap modifier for &alpha
Bi-2212 and Y123 highly curved single-crystal-like objects: whiskers, bows and ring-like structures
2012
High-temperature superconducting objects of Bi2Sr2CaCu2O8 and Y Ba2Cu3O7 highly curved in the ab-plane, such as curved/kinked whiskers, bows and ring-like structures, were obtained within a solid?liquid?solid (SLS) grass-like growth mechanism. As-grown objects are crystals with three-dimensional epitaxy similar to conventional single crystals: they can be viewed as crystal parts ?cut? from a conventional rectangular crystal. Between our curved objects and conventional crystals, whiskers or thin films there are some differences in the superconducting properties induced only by the shape factors and no new physics is observed. Some details of the growth mechanism are discussed, emphasizing cu…
Pd2Au36(SR)(24) cluster: structure studies
2015
The location of the Pd atoms in Pd2Au36(SC2H4Ph)(24), is studied both experimentally and theoretically. X-ray photoelectron spectroscopy (XPS) indicates oxidized Pd atoms. Palladium K-edge extended X-ray absorption fine-structure (EXAFS) data clearly show Pd-S bonds, which is supported by far infrared spectroscopy and by comparing theoretical EXAFS spectra in R space and circular dichroism spectra of the staple, surface and core doped structures with experimental spectra.
Gallium preference for the occupation of tetrahedral sites in Lu3(Al5-xGax)O12multicomponent garnet scintillators according to solid-state nuclear ma…
2019
Abstract In this study, the distributions of aluminum and gallium atoms over the tetrahedral and octahedral sites in the garnet structure were investigated in mixed Lu3Al5-xGaxO12 crystals by using 27Al and 71Ga magic angle spinning nuclear magnetic resonance (NMR) and single crystal 71Ga NMR. The experimental study was supported by theoretical calculations based on density functional theory (DFT) in order to predict the trends in terms of the substitutions of Al by Ga in the mixed garnets. Both the experimental and theoretical results indicated the non-uniform distribution of Al and Ga over the tetrahedral and octahedral sites in the garnet structure, with a strong preference for Ga occupy…
Measuring optical anisotropy in poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) films with added graphene
2015
Abstract Graphene is a 2D nanomaterial having a great potential for applications in electronics and optoelectronics. Composites of graphene with conducting polymers have shown high performance in practical devices and their solution-processability enables low-cost and high-throughput mass manufacturing using printing techniques. Here we measure the effect of incorporation of graphene into poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to the optical anisotropy, absorbance and conductivity of the film. Uniaxial anisotropy in PEDOT:PSS films has been thought to be caused by the spin-coating process used in fabrication. We have characterized spray- and spin-coated films …
Terahertz Spin‐to‐Charge Conversion by Interfacial Skew Scattering in Metallic Bilayers
2021
The efficient conversion of spin to charge transport and vice versa is of major relevance for the detection and generation of spin currents in spin‐based electronics. Interfaces of heterostructures are known to have a marked impact on this process. Here, terahertz (THz) emission spectroscopy is used to study ultrafast spin‐to‐charge‐current conversion (S2C) in about 50 prototypical F|N bilayers consisting of a ferromagnetic layer F (e.g., Ni81Fe19, Co, or Fe) and a nonmagnetic layer N with strong (Pt) or weak (Cu and Al) spin‐orbit coupling. Varying the structure of the F/N interface leads to a drastic change in the amplitude and even inversion of the polarity of the THz charge current. Rem…
BODIPY atropisomer interconversion, face discrimination, and superstructure appending
2016
International audience; A strategy was developed to append sterically hindered apical pickets on both faces of the BODIPY platform to prevent stacking and aggregation. Ortho-substitution of both the meso-phenyl ring and the boron-bound catechol affords the right directionality to append pickets, achieve face discrimination, featuring two inter-convertible atropisomers, and is reminiscent of the picket-fence strategy in porphyrins.