44,386 research outputs found
Program to develop an inorganic separator for a high temperature silver-zinc battery Quarterly progress report, 29 Apr. - 29 Jul. 1966
Inorganic separator for high temperature silver-zinc batter
Few layer graphene on SiC, pyrolitic graphite and graphene: a Raman scattering study
The results of micro-Raman scattering measurements performed on three
different ``graphitic'' materials: micro-structured disks of highly oriented
pyrolytic graphite, graphene multi-layers thermally decomposed from carbon
terminated surface of 4H-SiC and an exfoliated graphene monolayer are
presented. Despite its multi-layer character, most parts of the surface of the
graphitized SiC substrates shows a single-component, Lorentzian shape, double
resonance Raman feature in striking similarity to the case of a single graphene
monolayer. Our observation suggests a very weak electronic coupling between
graphitic layers on the SiC surface, which therefore can be considered to be
graphene multi-layers with a simple (Dirac-like) band structure.Comment: 4 pages, 3 Figures Structure of the paper strongly modified, small
changes in Fig 2 and 3. Same interpretation and same result
Parity Effect in a Small Superconducting Particle
Matveev and Larkin calculated the parity effect on the ground state energy of
a small superconducting particle in the regimes where the mean level spacing is
either large or small compared to the bulk gap. We perform a numerical
calculation which extends their results into the intermediate regime, where the
level spacing is of the same order as the bulk gap.Comment: 6 LaTeX pages, including 2 EPS figures; corrected reference and
spellin
Analytical solution of the equation of motion for a rigid domain wall in a magnetic material with perpendicular anisotropy
This paper reports the solution of the equation of motion for a domain wall
in a magnetic material which exhibits high magneto-crystalline anisotropy.
Starting from the Landau-Lifschitz-Gilbert equation for field-induced motion,
we solve the equation to give an analytical expression, which specifies the
domain wall position as a function of time. Taking parameters from a Co/Pt
multilayer system, we find good quantitative agreement between calculated and
experimentally determined wall velocities, and show that high field uniform
wall motion occurs when wall rigidity is assumed.Comment: 4 pages, 4 figure
Optical properties of periodic systems within the current-current response framework: pitfalls and remedies
We compare the optical absorption of extended systems using the
density-density and current-current linear response functions calculated within
many-body perturbation theory. The two approaches are formally equivalent for a
finite momentum of the external perturbation. At
, however, the equivalence is maintained only if a small
expansion of the density-density response function is used. Moreover, in
practical calculations this equivalence can be lost if one naively extends the
strategies usually employed in the density-based approach to the current-based
approach. Specifically we discuss the use of a smearing parameter or of the
quasiparticle lifetimes to describe the finite width of the spectral peaks and
the inclusion of electron-hole interaction. In those instances we show that the
incorrect definition of the velocity operator and the violation of the
conductivity sum rule introduce unphysical features in the optical absorption
spectra of three paradigmatic systems: silicon (semiconductor), copper (metal)
and lithium fluoride (insulator). We then demonstrate how to correctly
introduce lifetime effects and electron-hole interactions within the
current-based approach.Comment: 17 pages, 6 figure
Single parameter testing Quarterly report
Test signals, AC analysis, transfer function determination, and nonlinear components for single parameter testing of amplifie
Single parameter testing, phase D Final report
Single parameter testing techniques for electronic measuring equipment and other component
Doping nature of native defects in 1T-TiSe2
The transition metal dichalcogenide 1T-TiSe2 is a quasi two-dimensional
layered material with a charge density wave (CDW) transition temperature of
TCDW 200 K. Self-doping effects for crystals grown at different temperatures
introduce structural defects, modify the temperature dependent resistivity and
strongly perturbate the CDW phase. Here we study the structural and doping
nature of such native defects combining scanning tunneling
microscopy/spectroscopy and ab initio calculations. The dominant native single
atom dopants we identify in our single crystals are intercalated Ti atoms, Se
vacancies and Se substitutions by residual iodine and oxygen.Comment: 5 pages, 3 figure
On-Shell Unitarity Bootstrap for QCD Amplitudes
We describe the recently developed on-shell bootstrap for computing one-loop
amplitudes in non-supersymmetric theories such as QCD. The method combines the
unitarity method with loop-level on-shell recursion. The unitarity method is
used to compute cut-containing parts of amplitudes, and on-shell recursion is
used for the remaining rational terms.Comment: 10 pages, 9 figures, write-up of talks given by Z. Bern and D. A.
Kosower at Loops & Legs 2006, Eisenach, Germany; v2: added referenc
Spatio-Temporal Scaling of Solar Surface Flows
The Sun provides an excellent natural laboratory for nonlinear phenomena. We
use motions of magnetic bright points on the solar surface, at the smallest
scales yet observed, to study the small scale dynamics of the photospheric
plasma. The paths of the bright points are analyzed within a continuous time
random walk framework. Their spatial and temporal scaling suggest that the
observed motions are the walks of imperfectly correlated tracers on a turbulent
fluid flow in the lanes between granular convection cells.Comment: Now Accepted by Physical Review Letter
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