Influence of multi-orbital hopping and anisotropy in intra and inter orbital Coulomb interactions on the electronic spectra in iron pnictide superconductors

• Analysis of spectral function within BCS mean- field approximation.
• The various orbital hopping parameters, onsite Coulomb interactions and Hund’s orbital coupling control the electronic states at different k-point of Brillouin zone in superconducting state.
• Hund’s coupling energy and Coulomb correlations show opposite influence on spectral weight as also viewed in terms of ARPES measurement.

The present work deals with a theoretical study of the electronic spectral function in iron pnictide superconductors, like LaFeAs(O, F) material. We have attempted three orbital per site model Hamiltonian containing various orbitals hopping energies, onsite intra and inter orbital electronic correlations, and Hund’s coupling energy in Fe 3d orbitals. The expression of single particle spectral function within mean-field Green’s function approach for superconducting state of iron pnictides, is obtained. The single particle spectral function is numerically analyzed for extended s-wave pairing symmetry as a function of various model parameters applicable for these systems. It is pointed out that the nature of electronic states at different k-point of Brillouin zone is essentially influenced by various orbital hopping parameters, onsite Coulomb interaction and Hund’s orbital coupling. At X(0, π) point of Brillouin zone a well-defined three peak spectra is predicted while at Γ(0, 0) and M(π, π) point the electronic spectra show two peaks due to crossing of electronic state (at Γ-point). Our analysis also indicates that Hund’s coupling pile up the spectral weight close to Fermi level and onsite Coulomb correlations suppress the electronic states close to Fermi level at Γ(0, 0) point and show opposite influence on spectral weight at different location of Brillouin zone. Finally, the theoretically obtained behavior of single particle spectral function has been viewed in terms of recent photoemission ARPES measurements and existing theoretical results on electronic structure in iron pnictide superconductors.