97 research outputs found
Intercalant-Driven Superconductivity in YbC and CaC
Recently deiscovered superconductivity in YbC and CaC at temperatures
substantially higher than previously known for intercalated graphites, raised
several new questions: (1) Is the mechanism considerably different from the
previously known intercalated graphites? (2) If superconductivity is
conventional, what are the relevant phonons? (3) Given extreme similarity
between YbC and CaCa, why their critical temperatures are so different?
We address these questions on the basis of first-principles calculations and
conclude that coupling with intercalant phonons is likely to be the main force
for superconductivity in YbC and CaC, but not in alkaline-intercalated
compounds, and explain the difference in by the ``isotope effect'' due to
the difference in Yb and Ca atomic masses.Comment: 4 pages, embedded postscript figire
Applications of high repetition rate tabletop soft X-ray lasers become a reality in several fields
Includes bibliographical references (page 468).For many years researchers have envisioned the development of compact high repetition rate tabletop soft x-ray laser, that could be routinely used in application in numerous disciplines. With demonstrated average powers of several mW and millijoule-level pulse energy at 46.9nm, the Ne-like Ar capillary discharge-pumped laser is the first compact laser to reach this goal. In this paper we summarize the development status of high repetition rate tabletop soft x-ray lasers based on capillary discharge excitation, and give examples of their successful use in several applications. Results of the use of a caprllary discharge pumped 46.9nm laser m dense plasma interferometry, soft x-ray reflectometry for the determination of optical constants, characterization of diffraction gratings, laser ablation of materials, and plasma generation are described. The observation of lasing at 52.9nm line in Ne-like Cl with output pulse energy up to 10 μJ is also reported
Continuous selections of multivalued mappings
This survey covers in our opinion the most important results in the theory of
continuous selections of multivalued mappings (approximately) from 2002 through
2012. It extends and continues our previous such survey which appeared in
Recent Progress in General Topology, II, which was published in 2002. In
comparison, our present survey considers more restricted and specific areas of
mathematics. Note that we do not consider the theory of selectors (i.e.
continuous choices of elements from subsets of topological spaces) since this
topics is covered by another survey in this volume
Effects of Crystal Structure and the On-Site Coulomb Interactions on the Electronic and Magnetic Structure of Pyrochlores MoO (A= Y, Gd, and Nd)
Being motivated by recent experimental studies, we investigate magnetic
structures of the Mo pyrochlores MoO (= Y, Nd, and Gd) and
their impact on the electronic properties. The latter are closely related with
the behavior of twelve Mo() bands, located near the Fermi level and
well separated from the rest of the spectrum. We use a mean-field Hartree-Fock
approach, which combines fine details of the electronic structure for these
bands, extracted from the conventional calculations in the local-density
approximation, the spin-orbit interaction, and the on-site Coulomb interactions
amongst the Mo(4d) electrons, treated in the most general rotationally
invariant form. The Coulomb repulsion U plays a very important role in the
problem, and the semi-empirical value U1.5-2.5 eV accounts simultaneously
for the metal-insulator (M-I) transition, the ferromagnetic (FM) - spin-glass
(SG) transition, and for the observed enhancement of the anomalous Hall effect
(AHE). The M-I transition is mainly controlled by . The magnetic structure
at the metallic side is nearly collinear FM, due to the double exchange
mechanism. The transition into the insulating state is accompanied by the large
canting of spin and orbital magnetic moments. The sign of exchange interactions
in the insulating state is controlled by the Mo-Mo distances. Smaller distances
favor the antiferromagnetic coupling, which preludes the SG behavior in the
frustrated pyrochlore lattice. Large AHE is expected in the nearly collinear FM
state, near the point of M-I transition, and is related with the unquenched
orbital magnetization at the Mo sites. We also predict large magneto-optical
effect in the same FM compounds.Comment: 26 pages, 17 figures (low resolution is used for Figs. 6, 8, and 9,
please contact directly if you need the originals), 1 tabl
Determination of XUV optical constants by reflectometry using a high-repetition rate 46.9-nm laser
Includes bibliographical references (pages 1500-1501).We report the measurement of the optical constants of Si, GaP, InP, GaAs, GaAsP, and Ir at a wavelength of 46.9nm (26.5 eV). The optical constants were obtained from the measurement of the variation of the reflectivity as a function of angle utilizing, as an illumination source, a discharge pumped 46.9-nm table-top laser operated at a repetition rate of 1 Hz. These measurements constitute the first application of an ultrashort wavelength laser to materials research
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