33 research outputs found
Evolution of Mid-gap States and Residual 3-Dimensionality in LaSrCuO
We have carried out extensive first principles doping-dependent computations
of angle-resolved photoemission (ARPES) intensities in LaSrCuO
(LSCO) over a wide range of binding energies. Intercell hopping and the
associated 3-dimensionality, which is usually neglected in discussing cuprate
physics, is shown to play a key role in shaping the ARPES spectra. Despite the
obvious importance of strong coupling effects (e.g. the presence of a lower
Hubbard band coexisting with mid-gap states in the doped insulator), we show
that a number of salient features of the experimental ARPES spectra are
captured to a surprisingly large extent when effects of -dispersion are
properly included in the analysis.Comment: 5 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
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
Paramagnon-induced dispersion anomalies in the cuprates
We report the self-energy associated with RPA magnetic susceptibility in the
hole-doped Bi_2Sr_2CuO_6 (Bi2201) and the electron-doped Nd_{2-x}Ce_xCuO_4
(NCCO) in the overdoped regime within the framework of a one-band Hubbard
model. Strong weight is found in the magnetic spectrum around (pi, 0) at about
360 meV in Bi2201 and 640 meV in NCCO, which yields dispersion anomalies in
accord with the recently observed `waterfall' effects in the cuprates.Comment: Submitted to PRL, Dec. 21, 2006; 4 eps figures, revte
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
Fermi pockets and correlation effects in underdoped YBa2Cu3O6.5
The detection of quantum oscillations in the electrical resistivity of
YBa2Cu3O6.5 provides direct evidence for the existence of Fermi surface pockets
in an underdoped cuprate. We present a theoretical study of the electronic
structure of YBa2Cu3O7-d (YBCO) aiming at establishing the nature of these
Fermi pockets, i.e. CuO2 plane versus CuO chain or BaO. We argue that electron
correlation effects, such as orbital-dependent band distortions and highly
anisotropic self-energy corrections, must be taken into account in order to
properly interpret the quantum oscillation experiments.Comment: A high-resolution version can be found at
http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/YBCO_OrthoII_LDA.pd
Raising Bi-O bands above the Fermi energy level of hole-doped BiSrCaCuO and other cuprate superconductors
The Fermi surface (FS) of BiSrCaCuO
(Bi2212) predicted by band theory displays Bi-related pockets around the
point, which have never been observed experimentally. We show that
when the effects of hole doping either by substituting Pb for Bi or by adding
excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi
energy () and the resulting first-principles FS is in remarkable accord
with measurements. With decreasing hole-doping the Bi-O bands drop below
and the system self-dopes below a critical hole concentration. Computations on
other Bi- as well as Tl- and Hg-based compounds indicate that lifting of the
cation-derived band with hole doping is a general property of the electronic
structures of the cuprates.Comment: 4 pages, 4 figures; PRL (2006, in press
Fermiology and electronic homogeneity of the superconducting overdoped cuprate Tl-2201 revealed by quantum oscillations
We report an angular quantum oscillation study of Tl_2Ba_2CuO_{6+delta} for
two different doping levels (Tc = 10K and 26 K) and determine the Fermi surface
size and topology in considerable detail. Our results show that Fermi liquid
behavior is not confined to the edge of the superconducting dome and is robust
up to at least T_c^{max}/3.5. Superconductivity is found to survive up to a
larger doping p_c = 0.31 than in La_{2-x}Sr_xCuO_4. Our data imply that
electronic inhomogeneity does not play a significant role in the loss of
superconductivity and superfluid density in overdoped cuprates, and point
towards a purely magnetic or electronic pairing mechanismComment: 4 page