Influence of Multi‐Orbitals and Hund's Coupling Induced Pseudogap on Specific Heat Jump in Iron‐Pnictide High T c Superconductors

Abstract

A three-orbital per site theoretical model study is attempted to analyze nature of specific heat in iron-based superconductors. Based on recent experimental data in these systems, it is found that Fe five 3d orbitals, Hund’s coupling and intra- and inter-electron orbital correlations play significant role in electronic properties of these systems. Thus, in present work, we employed model Hamiltonian, containing hopping between orbitals, Hund’s coupling and intra- and inter- orbital Coulomb interactions for iron pnictide. Employing Green’s function technique within BCS mean field approximation, expressions of superconducting energy gap parameter and quasiparticle energies are obtained. Considering these parameters, we calculated specific heat and analyzed its variation with temperature and other parameters of model Hamiltonian. Also, a pseudogap (PG) parameter, arising out of multi-orbitals’ Hund’s coupling, as supported by ARPES and STM experiments, is introduced. The expression of specific heat is numerically analyzed to pinpoint its variation below and above transition temperature (T c ). A self-consistent numerical analysis of the specific heat jump as a function of multi-orbital hopping, electron interactions and Hund’s coupling in terms of PG parameter is shown in detail. Finally, we compared outcomes with recent theoretical and experimental data available on specific heat variations in iron superconductors like LaOFeAs system. This article is protected by copyright. All rights reserved.