Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides

Abstract

Using a second-order perturbative Green's functions approach we determined the normal state spectral function A( k, ω) employing a minimal model for ferropnictides. Used before to study magnetic fluctuations and superconducting properties, it includes the two effective bands related to Fe-3d orbitals proposed by S. Raghu et al. [Phys. Rev. B 77, 220503 (R) (2008)], and local intra-and inter-orbital correlations for the effective orbitals. Here, we focus on the normal state electronic properties, in particular the temperature and doping dependence of the total density of states, A(ω), and of A( k, ω) in different Brillouin zone regions, comparing them with existing angle resolved photoemission spectroscopy (ARPES) and theoretical results. We obtain an asymmetric effect of electron and hole doping, quantitative agreement with the experimental chemical potential shifts, as well as spectral weight redistributions near the Fermi level with temperature consistent with the available experiments. In addition, we predict a non-trivial dependence of A(ω) with 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 Brillouin zone points, not probed by ARPES yet, where the largest non-trivial effects of temperature on the renormalization are predicted for the parent compounds.

Normal-state magnetotransport properties of β -FeSe superconductors

“…-We present magnetotransport results for the normal state of FeSe compounds, and compare them with those calculated as presented in the previous section. Using the optimal correlation value U = 3 eV, previously found to describe best other electronic properties of these compounds [12], we analize the dependence on temperature, doping and magnetic field H z = H, and compare our results with new experimental data and those of ref. [10], as well as with the results obtained assuming uncorrelated electrons.…”

“…( 1). The effect of local intra-and inter-orbital correlations in ferropnictides was previously studied [12,19,22]. It was found that the inter-orbital correlation was less relevant than the intra-orbital one.…”

“…where n iσ = c † iσ c iσ and N iσ = d † iσ d iσ , and i denotes the Fe-lattice sites. Since correlations in FeSe compounds are intermediate [12,[23][24][25][26][27], and mainly motivated by the fact that it had been possible to describe previous magnetotransport results in terms of a phenomenological model with two uncorrelated carrier bands [10], here we decided to use Hartree-Fock approximation (HF) for the correlations. A recent study of the effect of correlations in FeSe [27], which found no relevant qualitative differences employing density functional theory (DFT) calculations and DFT + DMFT (DFT with dynamical mean-field theory) for the FS and the low-energy spectral properties, provides further justification for the level of approximation we used.…”

“…We determined the HF renormalized band structure, and self-consistently calculated μ(T ) for total electron filling n of the two renormalized effective bands (see ref. [12] for details).…”

“…In this work, to study normal-state magnetotransport properties of β-FeSe superconductors, we propose to employ a minimal microscopic model, which includes two effective bands describing the low-energy electronic structure, as well as intra-and inter-orbital Coulomb interactions. Previously [12] we treated the model using perturbative techniques to determine the electron Green's functions and the temperature-dependent spectral density function. The kinetic energy part of the Hamiltonian is represented by the effective two-orbital model proposed by Raghu et al in ref.…”