16,137 research outputs found
Incoherent pair tunneling in the pseudogap phase of cuprates
Motivated by a recent experiment by Bergeal et al., we reconsider incoherent
pair tunneling in a cuprate junction formed from an optimally doped
superconducting lead and an underdoped normal metallic lead. We study the
impact of the pseudogap on the pair tunneling by describing fermions in the
underdoped lead with a model self-energy that has been developed to reproduce
photoemission data. We find that the pseudogap causes an additional temperature
dependent suppression of the pair contribution to the tunneling current. We
discuss consistency with available experimental data and propose future
experimental directions.Comment: 5 pages, 3 figure
Electronic Structure of Hyperkagome Na4Ir3O8
We investigate the electronic structure of the frustrated magnet Na4Ir3O8
using density functional theory. Due to strong spin-orbit coupling, the
hyperkagome lattice is characterized by a half-filled complex of states, making
it a cubic iridium analogue of the high temperature superconducting cuprates.
The implications of our results for this unique material are discussed.Comment: expanded discussion with extra figures - 6 pages, 10 figure
Spin Hamiltonian of Hyperkagome Na4Ir3O8
We derive the spin Hamiltonian for the quantum spin liquid Na4Ir3O8, and then
estimate the direct and superexchange contributions between near neighbor
iridium ions using a tight binding parametrization of the electronic structure.
We find a magnitude of the exchange interaction comparable to experiment for a
reasonable value of the on-site Coulomb repulsion. For one of the two tight
binding parametrizations we have studied, the direct exchange term, which is
isotropic, dominates the total exchange. This provides support for those
theories proposed to describe this novel quantum spin liquid that assume an
isotropic Heisenberg model.Comment: 9 pages, 4 figure
Renormalization of spectral lineshape and dispersion below Tc in Bi2Sr2CaCu2O8+d
Angle-resolved photoemission (ARPES) data in the superconducting state of
Bi2Sr2CaCu2O8+d show a kink in the dispersion along the zone diagonal, which is
related via a Kramers-Kronig analysis to a drop in the low-energy scattering
rate. As one moves towards (pi,0), this kink evolves into a spectral dip. The
occurrence of these anomalies in the dispersion and lineshape throughout the
zone indicate the presence of a new energy scale in the superconducting state.Comment: New Figure 3 with expanded discussio
Pressure distributions and oil-flow patterns for a swept circulation-control wing
Pressure distributions and photographs of oil flow patterns are presented for a circulation control wing. The model was an aspect ratio four semispan wing mounted on the side wall of the NASA Ames Transonic Wind Tunnel. The airfoil was a 20 percent thick ellipse, modified with circular leading and trailing edges of 4 percent radius, and had a 25.4 cm constant chord. This configuration does not represent a specific wing design, but is generic. A full span, tangetial, rearward blowing, circulation control slot was incorporated ahead of the trailing edge on the upper surface. The wing was tested at Mach numbers from 0.3 to 0.75 at sweep angle of 0 to 45 deg with internal to external pressure ratios of 1.0 to 3.0. Lift and pitching momemt coefficients were obtained from measured pressure distributions at five span stations. When the conventional corrections resulting from sweep angle are applied to the lift and moment of circulation control sections, no additional corrections are necessary to account for changes in blowing efficiency. This is demonstrated for an aft sweep angle of 45 deg. An empirical technique for estimating the downwash distribution of a swept wing was validated
Live sheep trade from Australia summary information for 1994
This report provide summary information about mortalities in sheep and cattle during sea transport
Temperature-Grid Coordinates For Treating Pulsations In The Hydrogen Ionization Zone
A temperature grid is used for the description of motion in the hydrogen ionization region (HIR). This means zones are labeled by temperature rather than mass. Outside the HIR, the conventional Lagrangian grid is used, with transitional coordinates at the boundaries. Although our final object is to apply this scheme to the nonlinear periodic integration problem, we have first constructed a linear version as a test. It is found that periods and growth rates agree very well with those calculated using pure Lagrangian coordinates, but the temperature grid scheme proves less sensitive to a reduction of zones in the HIR. This property is desirable for the nonlinear problem where zoning must necessarily be coarse. As a further test of the temperature grid, we formulate the linear work integral in the new coordinates and confirm the consistency of the growth rates. Finally, it is shown that the scheme is insensitive to a change in the manner in which the transition zones are treated
- …