Effects of Pair-Hopping Coupling on Properties of Multi-Band Iron-Based Superconductors

Abstract

A variety of superconducting materials exhibit multi-band behavior in a form of multicomponent Fermi surfaces. By using a two-band model with a pair hopping, we explain how the interband coupling affects the physical properties of multi-band superconductors. We determine the temperature dependence of the superconducting gap and the specific heat, which strongly diverge from the BCS-type behavior. The anisotropic gap for the system with the mixed gap symmetry is found. Additionally, the spectral function and density of states are significantly modified by the inter-orbital interactions. The results obtained for different symmetries of the order parameter are in a good agreement with the experimental findings for the iron-based superconductors and other multi-band systems.

Collective excitations in two-band superconductors

“…In the same time, the effect on the larger parameter Ψ 2 is not so significant -applying of the interband coupling slightly increases the critical temperature T c T c2 only. These results correspond to numerical solutions of self-consistent equations for superconducting gaps ∆ 1 and ∆ 2 in two-band systems with both s-wave and d-wave symmetries [14][15][16][17][18][19].…”

“…( 17), and the oscillations of the relative phase θ 1 − θ 2 between two SC condensates (for symmetrical condensates we have ∇θ 1 = −∇θ 2 ) with energy gap in spectrum determined by interband coupling -Eqs. (18,20,22), which can be identified as Leggett mode [28][29][30]. It should be noted, as we can see from Eqs.…”

Influence of Multi‐Orbitals and Hund's Coupling Induced Pseudogap on Specific Heat Jump in Iron‐Pnictide High Tc Superconductors

“…For examining the multi-orbital overlapping and electron correlations in electronic spectra of iron pnictides, some theoretical and experimental attempts [5][6][7][8][9][10][11][12][13][14][15][16][17] have been made but are not clearly explained yet. Experimentally, Chen et al [12] studied the electronic structure of iron pnictides/chalcogenides, and pointed out that in case of iron chalcogenides, three bands exist near the center of Brillouin zone (BZ) at Γ-point with different symmetries, while in case of iron pnictides, only two bands, which are centered around the hole-like pocket (Γ-point) and electron-like pocket (M point) of the BZ are found, respectively.…”

Editorial on Research Topic: High-Tc Superconductivity in Electron-Doped Iron Selenide and Related Compounds

“…This result could have bearing on the absence of magnetic order in the nematic phase of bulk FeSe, for example. Last, Andrzej Ptok, Konrad Kapcia and Przemysław Piekarz study a two-band model for iron superconductors that includes intra-band and interband coupling between Cooper pairs [15]. They notably find Cooper pair states in relative orbitals of mixed symmetry.…”