Is LaO${}_{1-x}$F${}_x$FeAs an electron-phonon superconductor ?

Abstract

In this paper we calculate the electron-phonon coupling of the newly-discovered superconductor LaO${}_{1-x}$F${}_x$FeAs from first-principles, using Density Functional Perturbation Theory. For pure LaOFeAs, the calculated electron-phonon coupling constant $\lambda =0.21$ and logarithmic-averaged frequency ${\omega }_{ln}=206K$, give a maximum $T_c$ of 0.8 K, using the standard Migdal-Eliashberg theory. For the $F-$doped compounds, we predict even smaller coupling constants, due to the strong suppression of the electronic Density of States at the Fermi level. To reproduce the experimental $T_c=26K$, a 5-6 times larger coupling constant would be needed. Our results indicate that electron-phonon coupling is not sufficient to explain superconductivity in the newly-discovered LaO${}_{1-x}$F${}_x$FeAs superconductor, probably due to the importance of strong correlation effects.

References in corpus (3)

• LaFeAsO${}_{1-x}$F${}_x$: A low carrier density superconductor near itinerant magnetism
• Doping-dependent Phase Diagram of LaO{\it M}As ({\it M}=V--Cu) and Electron-type Superconductivity near Ferromagnetic Instability
• Electron-phonon interaction in the three-band model

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