34,269 research outputs found
Accelerator measurement of the energy spectra of neutrons emitted in the interaction of 3-GeV protons with several elements
The application of time of flight techniques for determining the shapes of the energy spectra of neutrons between 20 and 400 MeV is discussed. The neutrons are emitted at 20, 34, and 90 degrees in the bombardment of targets by 3 GeV protons. The targets used are carbon, aluminum, cobalt, and platinum with cylindrical cross section. Targets being bombarded are located in the internal circulating beam of a particle accelerator
Material and doping dependence of the nodal and anti-nodal dispersion renormalizations in single- and multi-layer cuprates
In this paper we present a review of bosonic renormalization effects on
electronic carriers observed from angle-resolved photoemission spectra in the
cuprates. We specifically discuss the viewpoint that these renormalizations
represent coupling of the electrons to the lattice, and review how the wide
range of materials dependence, such as the number of CuO layers, and the
doping dependence can be straightforwardly understood as arising due to novel
electron-phonon coupling.Comment: 9 pages and 6 figures. Submitted as a review article for Advances in
Condensed Matter Physic
X-ray Insights into the Nature of Quasars with Redshifted Broad Absorption Lines
We present observations of seven broad absorption line (BAL)
quasars at -2.516 with redshifted BAL troughs (RSBALs). Five of our
seven targets were detected by in 4-13 ks exposures with ACIS-S. The
values, values, and spectral energy
distributions of our targets demonstrate they are all X-ray weak relative to
expectations for non-BAL quasars, and the degree of X-ray weakness is
consistent with that of appropriately-matched BAL quasars generally.
Furthermore, our five detected targets show evidence for hard X-ray spectral
shapes with a stacked effective power-law photon index of . These findings support the presence of heavy X-ray
absorption ( cm) in RSBAL quasars,
likely by the shielding gas found to be common in BAL quasars more generally.
We use these X-ray measurements to assess models for the nature of RSBAL
quasars, finding that a rotationally-dominated outflow model is favored while
an infall model also remains plausible with some stipulations. The X-ray data
disfavor a binary quasar model for RSBAL quasars in general.Comment: 11 pages, 5 figures, and 3 table
SU(4) Spin-Orbital Two-Leg Ladder, Square and Triangle Lattices
Based on the generalized valence bond picture, a Schwinger boson mean field
theory is applied to the symmetric SU(4) spin-orbital systems. For a two-leg
SU(4) ladder, the ground state is a spin-orbital liquid with a finite energy
gap, in good agreement with recent numerical calculations. In two-dimensional
square and triangle lattices, the SU(4) Schwinger bosons condense at
(\pi/2,\pi/2) and (\pi/3,\pi/3), respectively. Spin, orbital, and coupled
spin-orbital static susceptibilities become singular at the wave vectors, twice
of which the bose condensation arises at. It is also demonstrated that there
are spin, orbital, and coupled spin-orbital long-range orderings in the ground
state.Comment: 5 page
- …