67 research outputs found
Quasiparticle Electronic structure of Copper in the GW approximation
We show that the results of photoemission and inverse photoemission
experiments on bulk copper can be quantitatively described within
band-structure theory, with no evidence of effects beyond the
single-quasiparticle approximation. The well known discrepancies between the
experimental bandstructure and the Kohn-Sham eigenvalues of Density Functional
Theory are almost completely corrected by self-energy effects.
Exchange-correlation contributions to the self-energy arising from 3s and 3p
core levels are shown to be crucial.Comment: 4 pages, 2 figures embedded in the text. 3 footnotes modified and 1
reference added. Small modifications also in the text. Accepted for
publication in PR
Lifetime of d-holes at Cu surfaces: Theory and experiment
We have investigated the hole dynamics at copper surfaces by high-resolution
angle-resolved photoemission experiments and many-body quasiparticle GW
calculations. Large deviations from a free-electron-like picture are observed
both in the magnitude and the energy dependence of the lifetimes, with a clear
indication that holes exhibit longer lifetimes than electrons with the same
excitation energy. Our calculations show that the small overlap of d- and
sp-states below the Fermi level is responsible for the observed enhancement.
Although there is qualitative good agreement of our theoretical predictions and
the measured lifetimes, there still exist some discrepancies pointing to the
need of a better description of the actual band structure of the solid.Comment: 15 pages, 7 figures, 1 table, to appear in Phys. Rev.
Spin polarization of the L-gap surface states on Au(111)
The electron spin polarization (ESP) of the L-gap surface states on Au(111)
is investigated theoretically by means of first-principles electronic-structure
and photoemission calculations. The surface states show a large spin-orbit
induced in-plane ESP which is perpendicular to the in-plane wavevector, in
close analogy to a two-dimensional electron gas with Rashba spin-orbit
interaction. The surface corrugation leads to a small ESP component normal to
the surface, being not reported so far. The surface-states ESP can be probed
qualitatively and quantitatively by spin- and angle-resolved photoelectron
spectroscopy, provided that the initial-state ESP is retained in the
photoemission process and not obscured by spin-orbit induced polarization
effects. Relativistic photoemission calculations provide detailed information
on what photoemission set-ups allow to conclude from the photoelectron ESP on
that of the surface states.Comment: 22 pages with 8 figure
Angle resolved photoemission spectroscopy of Sr_2CuO_2Cl_2 - a revisit
We have investigated the lowest binding-energy electronic structure of the
model cuprate Sr_2CuO_2Cl_2 using angle resolved photoemission spectroscopy
(ARPES). Our data from about 80 cleavages of Sr_2CuO_2Cl_2 single crystals give
a comprehensive, self-consistent picture of the nature of the first
electron-removal state in this model undoped CuO_2-plane cuprate. Firstly, we
show a strong dependence on the polarization of the excitation light which is
understandable in the context of the matrix element governing the photoemission
process, which gives a state with the symmetry of a Zhang-Rice singlet.
Secondly, the strong, oscillatory dependence of the intensity of the Zhang-Rice
singlet on the exciting photon-energy is shown to be consistent with
interference effects connected with the periodicity of the crystal structure in
the crystallographic c-direction. Thirdly, we measured the dispersion of the
first electron-removal states along G->(pi,pi) and G->(pi,0), the latter being
controversial in the literature, and have shown that the data are best fitted
using an extended t-J-model, and extract the relevant model parameters. An
analysis of the spectral weight of the first ionization states for different
excitation energies within the approach used by Leung et al. (Phys. Rev. B56,
6320 (1997)) results in a strongly photon-energy dependent ratio between the
coherent and incoherent spectral weight. The possible reasons for this
observation and its physical implications are discussed.Comment: 10 pages, 8 figure
ARPES: A probe of electronic correlations
Angle-resolved photoemission spectroscopy (ARPES) is one of the most direct
methods of studying the electronic structure of solids. By measuring the
kinetic energy and angular distribution of the electrons photoemitted from a
sample illuminated with sufficiently high-energy radiation, one can gain
information on both the energy and momentum of the electrons propagating inside
a material. This is of vital importance in elucidating the connection between
electronic, magnetic, and chemical structure of solids, in particular for those
complex systems which cannot be appropriately described within the
independent-particle picture. Among the various classes of complex systems, of
great interest are the transition metal oxides, which have been at the center
stage in condensed matter physics for the last four decades. Following a
general introduction to the topic, we will lay the theoretical basis needed to
understand the pivotal role of ARPES in the study of such systems. After a
brief overview on the state-of-the-art capabilities of the technique, we will
review some of the most interesting and relevant case studies of the novel
physics revealed by ARPES in 3d-, 4d- and 5d-based oxides.Comment: Chapter to appear in "Strongly Correlated Systems: Experimental
Techniques", edited by A. Avella and F. Mancini, Springer Series in
Solid-State Sciences (2013). A high-resolution version can be found at:
http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Reviews/ARPES_Springer.pdf.
arXiv admin note: text overlap with arXiv:cond-mat/0307085,
arXiv:cond-mat/020850
Angle-resolved photoemission spectroscopy of the cuprate superconductors
This paper reviews the most recent ARPES results on the cuprate
superconductors and their insulating parent and sister compounds, with the
purpose of providing an updated summary of the extensive literature in this
field. The low energy excitations are discussed with emphasis on some of the
most relevant issues, such as the Fermi surface and remnant Fermi surface, the
superconducting gap, the pseudogap and d-wave-like dispersion, evidence of
electronic inhomogeneity and nano-scale phase separation, the emergence of
coherent quasiparticles through the superconducting transition, and many-body
effects in the one-particle spectral function due to the interaction of the
charge with magnetic and/or lattice degrees of freedom. The first part of the
paper introduces photoemission spectroscopy in the context of strongly
interacting systems, along with an update on the state-of-the-art
instrumentation. The second part provides a brief overview of the scientific
issues relevant to the investigation of the low energy electronic structure by
ARPES. The rest of the paper is devoted to the review of experimental results
from the cuprates and the discussion is organized along conceptual lines:
normal-state electronic structure, interlayer interaction, superconducting gap,
coherent superconducting peak, pseudogap, electron self energy and collective
modes. Within each topic, ARPES data from the various copper oxides are
presented.Comment: Reviews of Modern Physics, in press. A HIGH-QUALITY pdf file is
available at http://www.physics.ubc.ca/~damascel/RMP_ARPES.pd
- …