Contrast of LiFeAs with Isostructural, Isoelectronic, and Non-superconducting MgFeGe

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概要

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• Stoichiometric LiFeAs at ambient pressure is an 18 K superconductor while isostructural, isoelectronic MgFeGe does not superconduct, despite their extremely similar electronic structures. To investigate possible sources of this distinctively different superconducting behavior, we quantify the differences using first principles density functional theory. Total Fe 3d occupations are identical, with individual 3d orbital occupations differing by no more than 0.015. However, a redistribution of bands just above the Fermi level \varepsilon_{\text{F}} provides an important distinction, with more Fe-derived states within 0.5 eV of the Fermi level and a higher N(\varepsilon_{\text{F}}) in MgFeGe. For many mechanisms these features would enhance the tendency toward superconductivity by providing more Cooper pairs (in MgFeGe), but the tendency toward magnetic instability might be more important. Two of the five Fermi surfaces differ between LiFeAs and MgFeGe, but still lead to similar q-dependencies of susceptibilities \chi_{0}(\mathbf{q}) including the familiar broad peak at (\pi,\pi). The larger \chi_{0}(\mathbf{q}) in MgFeGe, by 10--15% throughout the zone, leads us to tentatively identify this proximity to magnetic instability as the feature underlying the absence of superconductivity in MgFeGe. Another significant difference is the 2.5% difference of the in-plane lattice constant, positioning LiFeAs as a chemically compressed version of MgFeGe. This has possible significance since certain Fe pnictides display pressure-induced superconductivity.

• 2013-03-15

著者

• PICKETT Warren

  Department of Physics, University of California

• Pickett Warren

  Department of Physics, University of California, Davis, CA 95616, U.S.A.

• Rhee H.

  Department of Physics, University of California, Davis, CA 95616, U.S.A.

関連論文

• Exchange Coupling in Eu Monochalcogenides from First Principles(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)
• Contrast of LiFeAs with Isostructural, Isoelectronic, and Non-superconducting MgFeGe
• Contrast of LiFeAs with Isostructural, Isoelectronic, and Non-superconducting MgFeGe

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