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 $A(\vec{k},\omega)$ 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, $A(\omega)$, and of $A(\vec{k},\omega)$ 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 LaO1−x_{1-x}Fx_{x}BiS2_{2} superconductors

A good description of the electronic structure of BiS$_{2}$-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 LaO$_{1-x}$F$_{x}$BiS$_{2}$, 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-($p_{Y}$, $p_{X}$) and S-($p_{Y}$, $p_{X}$) 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 LaO$_{1-x}$F$_{x}$BiS$_{2}$, 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 LaO$_{1-x}$F$_{x}$BiS$_{2}$. Our analytical approximation enabled us to calculate the spectral density around the conduction band minimum at $\vec{k}_{0}=(0.45\pi,0.45\pi)$, 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