1,118 research outputs found
Failure of t-J models in describing doping evolution of spectral weight in x-ray scattering, optical and photoemission spectra of the cuprates
We have analyzed experimental evidence for an anomalous transfer of spectral
weight from high to low energy scales in both electron and hole doped cuprates
as a function of doping. X-ray scattering, optical and photoemission spectra
are all found to show that the high energy spectral weight decreases with
increasing doping at a rate much faster than predictions of the large limit
calculations. The observed doping evolution is however well-described by an
intermediate coupling scenario where the effective Hubbard is comparable to
the bandwidth. The experimental spectra across various spectroscopies are
inconsistent with fixed- exact diagonalization or quantum Monte Carlo
calculations, and suggest a significant doping dependence of the effective
in the cuprates.Comment: Accepted for Phys. Rev. B (2010). 7 pages, 4 figure
Influence of the Third Dimension of Quasi-Two-Dimensional Cuprate Superconductors on Angle-Resolved Photoemission Spectra
Angle-resolved photoemission spectroscopy (ARPES) presents significant
simplications in analyzing strictly two-dimensional (2D) materials, but even
the most anisotropic physical systems display some residual
three-dimensionality. Here we demonstrate how this third dimension manifests
itself in ARPES spectra of quasi-2D materials by considering the example of the
cuprate BiSrCaCuO (Bi2212). The intercell, interlayer
hopping, which is responsible for -dispersion of the bands, is found to
induce an irreducible broadening to the ARPES lineshapes with a characteristic
dependence on the in-plane momentum . Our study suggests that
ARPES lineshapes can provide a direct spectroscopic window for establishing the
existence of coherent c-axis conductivity in a material via the detection of
this new broadening mechanism, and bears on the understanding of 2D to 3D
crossover and pseudogap and stripe physics in novel materials through ARPES
experiments.Comment: 5 pages, 4 figure
Induced superconductivity in noncuprate layers of the BiSrCaCuO high-temperature superconductor: Modeling of scanning tunneling spectra
We analyze how the coherence peaks observed in Scanning Tunneling
Spectroscopy (STS) of cuprate high temperature superconductors are transferred
from the cuprate layer to the oxide layers adjacent to the STS microscope tip.
For this purpose, we have carried out a realistic multiband calculation for the
superconducting state of BiSrCaCuO (Bi2212) assuming a
short range d-wave pairing interaction confined to the nearest-neighbor Cu
orbitals. The resulting anomalous matrix elements of the Green's
function allow us to monitor how pairing is then induced not only within the
cuprate bilayer but also within and across other layers and sites. The symmetry
properties of the various anomalous matrix elements and the related selection
rules are delineated.Comment: 9 pages, 2 figures. Accepted for publication in Phys. Rev.
Nonmonotonic superconducting gap in electron-doped PrLaCeCuO: Evidence of coexisting antiferromagnetism and superconductivity?
Recent experiments on PrLaCeCuO observe an anisotropic
spin-correlation gap and a nonmonotonic superconducting (SC) gap, which we
analyze within the framework of a
model with a
pairing interaction including a third harmonic contribution. By
introducing a realistic broadening of the quasiparticle spectrum to reflect
small-angle scattering, our computations explain the experimental observations,
especially the presence of a maximum in the leading edge gap in the vicinity of
the hot-spots. Our analysis suggests that the material behaves like a {\it
two-band} superconductor with the d-wave third harmonic acting as the {\it
interband pairing gap}, and that the anti-ferromagnetic (AFM) and SC orders
co-exist in a uniform phase
Reconstructing the bulk Fermi surface and the superconducting gap properties from Neutron Scattering experiments
We develop an analytical tool to extract bulk electronic properties of
unconventional superconductors through inelastic neutron scattering (INS)
spectra. Since the spin excitation spectrum in the superconducting (SC) state
originates from Bogoliubov quasiparticle scattering associated with Fermi
surface nesting, its energy-momentum relation--the so called `hour-glass'
feature--can be inverted to reveal the Fermi momentum dispersion of the
single-particle spectrum as well as the corresponding SC gap function. The
inversion procedure is analogous to the quasiparticle interference (QPI) effect
in scanning tunneling microscopy (STM). Whereas angle-resolved photoemission
spectroscopy (ARPES) and STM provide surface sensitive information, our
inversion procedure provides bulk electronic properties. The technique is
essentially model independent and can be applied to a wide variety of
materials.Comment: 8 pages, 4 figure
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