46 research outputs found
Coupling angle resolved photoemission data and quasiparticle structure in antiferromagnetic insulators Sr2CuO2Cl2 and Ca2CuO2Cl2
We have analyzed the quasiparticle dispersion and ARPES-spectral density for
Sr2CuO2Cl2 and Ca2CuO2Cl2 antiferromagnetic insulators along basic symmetric
directions of the Brillouin zone (BZ) in a framework of an extended tight
binding method (ETBM) with explicit account for intracell strong electron
correlations. The quasiparticle dispersion is in a good agreement with ARPES-
data. At the top of valence band we found a narrow impurity-like virtual level
with the spectral weight proportional to the concentration of spin
fluctuations. A pseudogap between the virtual level and the top of the valence
band has dispersion similar to 'remnant Fermi surface' in Ca2CuO2Cl2 and to a
pseudogap in the underdoped Bi2212 samples. A calculated parity of the
polarized ARPES-spectra in (0,0),(pi/2,pi/2),(pi,0) - points in the AFM- phase
is even with regard to relative magnitudes of the partial contributions by
different orbitals to the total ARPES- spectral density. Conditions of an
observability for the different partial contributions in the polarized ARPES-
experiments are determined also.Comment: 15 pdf-pages with 10 figures and tabl
The t-J model on a semi-infinite lattice
The hole spectral function of the t-J model on a two-dimensional
semi-infinite lattice is calculated using the spin-wave and noncrossing
approximations. In the case of small hole concentration and strong
correlations, , several near-boundary site rows appear to be depleted
of holes. The reason for this depletion is a deformation of the magnon cloud,
which surrounds the hole, near the boundary. The hole depletion in the boundary
region leads to a more complicated spectral function in the boundary row in
comparison with its bulk shape.Comment: 8 pages, 5 figure
Strong spin triplet contribution of the first removal state in the insulating regime of Bi2Sr2Ca1-xYxCu2O8+delta
The experimental dispersion of the first removal state in the insulating
regime of Bi2Sr2Ca1-xYxCu2O8+delta is found to differ significantly from that
of other parent materials: oxyclorides and La2CuO4 . For Y-contents of 0.92 > x
> 0.55 due to nonstoichiometric effects in the Bi-O layers, the hole
concentration in the CuO2 -layers is almost constant and on the contrary the
crystal lattice parameters a,b,c change very strongly. This (a,b) parameter
increase and c parameter decrease results in an unconventional three peak
structure at (0,0);(pi/2, pi/2);(pi,pi) for x=0.92. We can describe the
experimental data only beyond the framework of the 3-band pd-model involving
the representations of a new triplet counterpart for the Zhang-Rice singlet
state.Comment: 16 pages, 4 figure
Parameters of the Effective Singlet-Triplet Model for Band Structure of High- Cuprates by Different Approaches
The present paper covers the problem of parameters determination for
High- superconductive copper oxides. Different approaches, {\it ab initio}
LDA and LDA+U calculations and Generalized Tight-Binding (GTB) method for
strongly correlated electron systems, are used to calculate hopping and
exchange parameters of the effective singlet-triplet model for -layer.
The resulting parameters are in remarkably good agreement with each other and
with parameters extracted from experiment. This set of parameters is proposed
for proper quantitative description of physics of hole doped High-
cuprates in the framework of effective models.Comment: PACS 74.72.h; 74.20.z; 74.25.Jb; 31.15.A
The Fermi surface and the role of electronic correlations in SmCeCuO
Using LDA+GTB (local density approximation+generalized tight-binding) hybrid
scheme we investigate the band structure of the electron-doped high-
material SmCeCuO. Parameters of the minimal tight-binding
model for this system (the so-called 3-band Emery model) were obtained within
the NMTO (-th order Muffin-Tin orbital) method. Doping evolution of the
dispersion and Fermi surface in the presence of electronic correlations was
investigated in two regimes of magnetic order: short-range (spin-liquid) and
long-range (antiferromagnetic metal). Each regime is characterized by the
specific topologies of the Fermi surfaces and we discuss their relation to
recent experimental data.Comment: 10 pages, 4 figures, 1 table, Published versio