2008/11/30 by Takuji Nomura · 1 citation
Business, Management and Accounting · Materials Science · Physics and Astronomy · #Condensed matter physics #Corporate Taxation and Avoidance #Coulomb #Eigenvalues and eigenvectors #Electron #Electronic band structure #Hubbard model #Iron-based superconductors research #Pairing #Perturbation theory (quantum mechanics) #Physics #Quantum mechanics #Superconductivity #Symmetry (geometry) #cond-mat.str-el #cond-mat.supr-con #t-J model
paper · pdf · doi:10.1143/jpsj.78.034716
published as J. Phys. Soc. Jpn. 78 (2009) 034716 · 24 pages, 9 figures
openalex publication_date 2009/03/10 · arxiv created 2009/03/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The high-transition-temperature (high-Tc) superconductivity discovered recently in iron pnictides is analyzed within a perturbation theory. Specifically, the probable pairing symmetry, the doping dependence of the transition temperature and the pairing mechanism are studied by solving the Eliashberg equation for multi-band (2- and 5-band) Hubbard models with realistic electronic structures. The effective pairing interaction is expanded perturbatively in the on-site Coulomb integrals up to third order. Our perturbative weak-coupling approach shows that sufficiently large eigenvalues of the Eliashberg equation are obtained to explain the actual high transition temperatures by taking realistic on-site Coulomb integrals in the 5-band model. Thus, unconventional (non-phonon-mediated) superconductivity is highly likely to be realized. The superconducting order parameter does not change its sign on the Fermi surfaces, but it does change between the electron and hole Fermi surfaces. Consequently, the probable pairing symmetry is always "a nodeless extended s-wave symmetry (more specifically, an s+--wave symmetry)" over the whole parameter region that we investigated. It is suggested that the 2-band model is insufficient to explain the high values of Tc.