The Unprecedented Giant Coupling of Fe-spin State and the As-As Hybridization in Iron-Pnictide
Abstract
Description
From first principles calculations we unravel surprisingly strong interactions between arsenic ions in iron-pnictides, the strength of which is controlled by the Fe-spin state. Reducing the Fe-magnetic moment, weakens the Fe-As bonding, and in turn, increases As-As interactions, causing giant reduction in the c-axis. For CaFe$_2$As$_2$ system, this reduction is as large as 1.4 Å. Since the large c-reduction has been recently observed only under high-pressure\cite{cTphase}, our results suggest that the iron magnetic moment should be present in Fe-pnictides at all times at ambient pressure. Finally, the conventional electron-phonon coupling in the collapsed phase of CaFe$_2$As$_2$ gives a maximum $T_c$ of 0.6 K and can not explain the $\sim12$ K superconductivity observed in some experiments. Implications of these findings on the mechanism of superconductivity in iron-pnictides are discussed.
Published version with updated references. It has new results such as conventional e-ph coupling in the collapsed phase of CaFe2As2 gives a maximum Tc of 0.6 K and cannot explain the ~12 K superconductivity observed in some experiments. Implications of these findings on the mechanism of superconductivity in iron pnictides are discussed
Published version with updated references. It has new results such as conventional e-ph coupling in the collapsed phase of CaFe2As2 gives a maximum Tc of 0.6 K and cannot explain the ~12 K superconductivity observed in some experiments. Implications of these findings on the mechanism of superconductivity in iron pnictides are discussed