1,265 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
Effect of Hole Doping on the Electronic Structure of Tl2201
We discuss doping dependencies of the electronic structure and Fermi surface
of the monolayer TlCuBaCuO (Tl2201). The TlO bands
are found to be particularly sensitive to doping in that these bands rapidly
move to higher energies as holes are added into the system. Such doping effects
beyond the rigid band picture should be taken into account in analyzing and
modeling the electronic spectra of the cuprates.Comment: 2 pages, Submitted to Physica C / Proceedings of the M2S-HTSC-VIII
Conferenc
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.
Matrix Element and Strong Electron Correlation Effects in ARPES from Cuprates
We discuss selected results from our recent work concerning the ARPES
(angle-resolved photoemission) spectra from the cuprates. Our focus is on
developing an understanding of the effects of the ARPES matrix element and
those of strong electron correlations in analyzing photointensities. With
simulations on BiSrCaCuO (Bi2212), we show that the
ARPES matrix element possesses remarkable selectivity properties, such that by
tuning the photon energy and polarization, emission from the bonding or the
antibonding states can be enhanced. Moreover, at low photon energies (below 25
eV), the Fermi surface (FS) emission is dominated by transitions from just the
O-atoms in the CuO planes. In connection with strong correlation effects,
we consider the evolution with doping of the FS of
NdCeCuO (NCCO) in terms of the -- Hubbard
model Hamiltonian. We thus delineate how the FS evolves on electron doping from
the insulating state in NCCO. The Mott pseudogap is found to collapse around
optimal doping suggesting the existence of an associated quantum critical
point.Comment: 5 pages, 4 figures, accepted to be published in Journal of Physics
and Chemistry of Solid
Renormalization of f-levels away from the Fermi energy in electron excitation spectroscopies: Density functional results of NdCeCuO
Relaxation energies for photoemission, when an occupied electronic state is
excited, and for inverse photoemission, when an empty state is filled, are
calculated within the density functional theory with application to
NdCeCuO. The associated relaxation energies are obtained by
computing differences in total energies between the ground state and an excited
state in which one hole or electron is added into the system. The relaxation
energies of f-electrons are found to be of the order of several eV's,
indicating that f-bands will appear substantially away from the Fermi energy
() in their spectroscopic images, even if these bands lie near . Our
analysis explains why it would be difficult to observe f electrons at the
even in the absence of strong electronic correlations.Comment: 6 pages, 1 figure, 1 tabl
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