398 research outputs found
Metal-semiconductor (semimetal) superlattices on a graphite sheet with vacancies
It has been found that periodically closely spaced vacancies on a graphite
sheet cause a significant rearrange-ment of its electronic spectrum: metallic
waveguides with a high density of states near the Fermi level are formed along
the vacancy lines. In the direction perpendicular to these lines, the spectrum
exhibits a semimetal or semiconductor character with a gap where a vacancy
miniband is degenerated into impurity levels.Comment: 4 pages, 3 figure
Ferromagnetism in the Mott insulator Ba2NaOsO6
Results are presented of single crystal structural, thermodynamic, and
reflectivity measurements of the double-perovskite Ba2NaOsO6. These
characterize the material as a 5d^1 ferromagnetic Mott insulator with an
ordered moment of ~0.2 Bohr magnetons per formula unit and TC = 6.8(3) K. The
magnetic entropy associated with this phase transition is close to Rln2,
indicating that the quartet groundstate anticipated from consideration of the
crystal structure is split, consistent with a scenario in which the
ferromagnetism is associated with orbital ordering.Comment: 5 pages, 5 figures, added reference
Towards an Abelian Formulation of Lattice QCD Confinement
We probe for operators occurring in the APQCD(``abelian-projected QCD'')
action by evaluating abelian-projected -plaquette spectral densities in pure
gauge fixed to maximal abelian gauge. Couplings are
extracted from the spectral densities for each representation ,
plaquette. While APQCD is dominated by a resonance, we also find
evidence for weakly coupled plaquettes. Moreover, since even if , plaquettes must be
significant since APQCD is confining.Comment: 1+11 pages, fixed minor postscript erro
Synthesis, Structure and Conductivity of Solid Solutions Based on La2ZnAlO5.5 Doped with CaO
This paper devoted to the synthesis and investigation of physico-chemical properties of solid solutions based on new perovskite La2ZnAlO5.5. The solid state synthesis of calcium-doped samples were realized. Structure, phase composition and conductivity of samples were investigated.This work was supported by the State Assignment no. АААА-А20-120061990010-7
Superlattices Consisting of "Lines" of Adsorbed Hydrogen Atom Pairs on Graphene
The structures and electron properties of new superlattices formed on
graphene by adsorbed hydrogen molecules are theoretically described. It has
been shown that superlattices of the (n, 0) zigzag type with linearly arranged
pairs of H atoms have band structures similar to the spectra of (n, 0) carbon
nanotubes. At the same time, superlattices of the (n, n) type with a
"staircase" of adsorbed pairs of H atoms are substantially metallic with a high
density of electronic states at the Fermi level and this property distinguishes
their spectra from the spectra of the corresponding (n, n) nanotubes. The
features of the spectra have the Van Hove form, which is characteristic of each
individual superlattice. The possibility of using such planar structures with
nanometer thickness is discussed.Comment: 5 pages, 4 figure
Identifying gravity waves launched by the Hunga Tonga-Hunga Ha‘apai volcanic eruption in mesosphere/lower thermosphere winds derived from CONDOR and the Nordic Meteor Radar Cluster
The Hunga Tonga-Hunga Ha‘apai volcano eruption was a unique event that caused many atmospheric phenomena around the globe. In this study, we investigate the atmospheric gravity waves in the mesosphere/lower thermosphere (MLT) launched by the volcanic explosion in the Pacific leveraging multistatic meteor radar observations from the Chilean Observation Network De Meteor Radars (CONDOR) and the Nordic Meteor Radar Cluster in Fennoscandia. MLT winds are computed using a recently developed 3DVAR+DIV algorithm. We found an eastward and a westward traveling gravity wave in the CONDOR zonal and meridional wind measurements, which arrived 12 hours and 48 hours after the eruption, and one in Nordic Meteor Radar Cluster that arrived 27.5 hours after the volcanic detonation. We obtained observed phase speeds for the eastward great circle path at both locations of about 250 m/s and 170–150 m/s for the opposite propagation direction. The intrinsic phase speed was estimated to be 200–212 m/s. Furthermore, we identified a potential lamb wave signature in the MLT winds using 5 minute resolved 3DVAR+DIV retrievals
Soliton pair creation in classical wave scattering
We study classical production of soliton-antisoliton pairs from colliding
wave packets in (1+1)-dimensional scalar field model. Wave packets represent
multiparticle states in quantum theory; we characterize them by energy E and
particle number N. Sampling stochastically over the forms of wave packets, we
find the entire region in (E,N) plane which corresponds to classical creation
of soliton pairs. Particle number is parametrically large within this region
meaning that the probability of soliton-antisoliton pair production in
few-particle collisions is exponentially suppressed.Comment: 16 pages, 8 figures, journal version; misprint correcte
Catalyzed decay of false vacuum in four dimensions
The probability of destruction of a metastable vacuum state by the field of a
highly virtual particle with energy is calculated for a (3+1) dimensional
theory in the leading WKB approximation in the thin-wall limit. It is found
that the induced nucleation rate of bubbles, capable of expansion, is
exponentially small at any energy. The negative exponential power in the rate
reaches its maximum at the energy, corresponding to the top of the barrier in
the bubble energy, where it is a finite fraction of the same power in the
probability of the spontaneous decay of the false vacuum, i.e. at .Comment: 9 pages (standard LaTeX)+ 3 figures (one figure in LaTeX, two are
appended in PostScript). TPI-MINN-92/31-
PHYSICOCHEMICAL CHARACTERIZATION OF RIBAVIRIN WITH SPECTROSCOPY AND MOLECULAR MODELING
This work was supported by Mendeleev University of Chemical Technology of Russia. Project Number K-003-2018
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