Interband superconductivity: contrasts between BCS and Eliashberg theory

Abstract

The newly discovered iron pnictide superconductors apparently present an unusual case of interband-channel pairing superconductivity. Here we show that, in the limit where the pairing occurs within the interband channel, several surprising effects occur quite naturally and generally: different density-of-states on the two bands lead to several unusual properties, including a gap ratio which behaves inversely to the ratio of density-of-states; the weak-coupling limit of the Eliashberg and the BCS theory, commonly taken as equivalent, in fact predict qualitatively different dependence of the ${\Delta }_1/{\Delta }_2$ and $\Delta /T_c$ ratios on coupling constants. We show analytically that these effects follow directly from the interband character of superconductivity. Our results show that in the interband-only pairing model the maximal gap ratio is $\sqrt{N_2/N_1}$ as strong-coupling effects act only to reduce this ratio. This suggests that if the large experimentally reported gap ratios (up to a factor 2) are correct, the pairing mechanism must include more intraband interaction than is usually assumed.

4 pages, 3 figures

References in corpus (8)

• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Electronic Structure, Electron-Phonon Coupling, and Multiband Effects in MgB2
• NMR relaxation rate in superconducting pnictides: extended $s_{\pm }$ scenario
• Properties of the superconducting state in a two-band model
• Possible pairing states of the Fe-based superconductors
• Critical temperature and giant isotope effect in presence of paramagnons
• Strong electron-phonon interaction in multiband superconductors

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