17,106 research outputs found
Mechanism of magnetism in stacked nanographite: Theoretical study
Nanographite systems, where graphene sheets of the orders of the nanometer
size are stacked, show novel magnetic properties, such as, spin-glass like
behaviors and the change of ESR line widths in the course of gas adsorptions.
We theoretically investigate stacking effects in the zigzag nanographite sheets
by using a tight binding model with the Hubbard-like onsite interactions. We
find a remarkable difference in the magnetic properties between the simple A-A
and A-B type stackings. For the simple stacking, there are not magnetic
solutions. For the A-B stacking, we find antiferromagnetic solutions for strong
onsite repulsions. The local magnetic moments tend to exist at the edge sites
in each layer due to the large amplitude of wavefunctions at these sites.
Relations with experiments are discussed.Comment: PACS numbers: 75.30.-m, 75.70.Cn, 75.10.Lp, 75.40.Mg; E-mail:
[email protected]; http://www.etl.go.jp/~harigaya/welcome_E.htm
A Nomographic Methodology for Use in Performance Trade-Off Studies of Parabolic Dish Solar Power Modules
A simple graphical method was developed to undertake technical design trade-off studies for individual parabolic dish models comprising a two-axis tracking parabolic dish with a cavity receiver and power conversion assembly at the focal point. The results of these technical studies are then used in performing the techno-economic analyses required for determining appropriate subsystem sizing. Selected graphs that characterize the performance of subsystems within the module were arranged in the form of a nomogram that would enable an investigator to carry out several design trade-off studies. Key performance parameters encompassed in the nomogram include receiver losses, intercept factor, engine rating, and engine efficiency. Design and operation parameters such as concentrator size, receiver type (open or windowed aperture), receiver aperture size, operating temperature of the receiver and engine, engine partial load characteristics, concentrator slope error, and the type of reflector surface, are also included in the graphical solution. Cost considerations are not included
Effect of disorder outside the CuO planes on of copper oxide superconductors
The effect of disorder on the superconducting transition temperature
of cuprate superconductors is examined. Disorder is introduced into the cation
sites in the plane adjacent to the CuO planes of two single-layer
systems, BiSrLnCuO and
LaNdSrCuO. Disorder is controlled by changing
rare earth (Ln) ions with different ionic radius in the former, and by varying
the Nd content in the latter with the doped carrier density kept constant. We
show that this type of disorder works as weak scatterers in contrast to the
in-plane disorder produced by Zn, but remarkably reduces suggesting
novel effects of disorder on high- superconductivity.Comment: 5 pages, 5 figures, to be published in Phys. Rev. Let
Neutron-scattering study of spin correlations in La1.94-xSrxCe0.06CuO4
We performed a neutron-scattering experiment to investigate the effect of
distortion of CuO2 planes on the low-energy spin correlation of
La1.94-xSrxCe0.06CuO4 (LSCCO). Due to the carrier-compensation effect by
co-doping of Sr and Ce, LSCCO has a smaller orthorhombic lattice distortion
compared to La2-xSrxCuO4 (LSCO) with comparable hole concentration p. A clear
gap with the edge-energy of 6~7 meV was observed in the energy spectrum of
local dynamical susceptibility c"(w) for both x=0.18 (p~0.14) and x=0.24
(p~0.20) samples as observed for optimally-doped LSCO (x=0.15~0.18). For the
x=0.14 (p~0.10) sample, in addition to the gap-like structure in c"(w) we
observed a low-energy component within the gap which develops below 2~3meV with
decreasing the energy. The low-energy component possibly coincides with the
static magnetic correlation observed in this sample. These results are
discussed from a view point of relationship between the stability of low-energy
spin fluctuations and the distortion of CuO2 planes.Comment: 4 pages, 3 figures, proceeding for SNS2007 conferenc
Direct Imaging of Spatially Modulated Superfluid Phases in Atomic Fermion Systems
It is proposed that the spatially modulated superfluid phase, or the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state could be observed in resonant
Fermion atomic condensates which are realized recently. We examine optimal
experimental setups to achieve it by solving Bogoliubov-de Gennes equation both
for idealized one-dimensional and realistic three-dimensional cases. The
spontaneous modulation of this superfluid is shown to be directly imaged as the
density profiles either by optical absorption or by Stern-Gerlach experiments.Comment: 4 pages, 3 figure
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