22,327 research outputs found
SL(2,R)-geometric phase space and (2+2)-dimensions
We propose an alternative geometric mathematical structure for arbitrary
phase space. The main guide in our approach is the hidden SL(2,R)-symmetry
which acts on the phase space changing coordinates by momenta and vice versa.
We show that the SL(2,R)-symmetry is implicit in any symplectic structure. We
also prove that in any sensible physical theory based on the SL(2,R)-symmetry
the signature of the flat target "spacetime" must be associated with either
one-time and one-space or at least two-time and two-space coordinates. We
discuss the consequences as well as possible applications of our approach on
different physical scenarios.Comment: 17 pages, no figure
Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides
Using a second-order perturbative Green's functions approach we determined
the normal state single-particle spectral function
employing a minimal effective model for iron-based superconductors. The
microscopic model, used before to study magnetic fluctuations and
superconducting properties, includes the two effective tight-binding bands
proposed by S.Raghu et al. [Phys. Rev. B 77, 220503 (R) (2008)], and intra- and
inter-orbital local electronic correlations, related to the Fe-3d orbitals.
Here, we focus on the study of normal state electronic properties, in
particular the temperature and doping dependence of the total density of
states, , and of in different Brillouin zone
regions, and compare them to the existing angle resolved photoemission
spectroscopy (ARPES) and previous theoretical results in ferropnictides. We
obtain an asymmetric effect of electron and hole doping, quantitative agreement
with the experimental chemical potential shifts as a function of doping, as
well as spectral weight redistributions near the Fermi level as a function of
temperature consistent with the available experimental data. In addition, we
predict a non-trivial dependence of the total density of states with the
temperature, exhibiting clear renormalization effects by correlations.
Interestingly, investigating the origin of this predicted behaviour by
analyzing the evolution with temperature of the k-dependent self-energy
obtained in our approach, we could identify a number of specific Brillouin zone
points, none of them probed by ARPES experiments yet, where the largest
non-trivial effects of temperature on the renormalization are present.Comment: Manuscript accepted in Physics Letters A on Feb. 25, 201
Normal state electronic properties of LaOFBiS superconductors
A good description of the electronic structure of BiS-based
superconductors is essential to understand their phase diagram, normal state
and superconducting properties. To describe the first reports of normal state
electronic structure features from angle resolved photoemission spectroscopy
(ARPES) in LaOFBiS, we used a minimal microscopic model to
study their low energy properties. It includes the two effective tight-binding
bands proposed by Usui et al [Phys.Rev.B 86, 220501(R)(2012)], and we added
moderate intra- and inter-orbital electron correlations related to Bi-(,
) and S-(, ) orbitals. We calculated the electron Green's
functions using their equations of motion, which we decoupled in second-order
of perturbations on the correlations. We determined the normal state spectral
density function and total density of states for LaOFBiS,
focusing on the description of the k-dependence, effect of doping, and the
prediction of the temperature dependence of spectral properties. Including
moderate electron correlations, improves the description of the few
experimental ARPES and soft X-ray photoemission data available for
LaOFBiS. Our analytical approximation enabled us to
calculate the spectral density around the conduction band minimum at
, and to predict the temperature dependence of
the spectral properties at different BZ points, which might be verified by
temperature dependent ARPES.Comment: 9 figures. Manuscript accepted in Physica B: Condensed Matter on Jan.
25, 201
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