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arXiv · 0807.3936

The Unprecedented Giant Coupling of Fe-spin State and the As-As Hybridization in Iron-Pnictide

T. Yildirim
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Abstract

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.

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T. Yildirim. 2009-02-19. The Unprecedented Giant Coupling of Fe-spin State and the As-As Hybridization in Iron-Pnictide. https://doi.org/10.1103/physrevlett.102.037003

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