Effects of metallic spacer in layered superconducting Sr2(Mg$_y$Ti$_{1-y}$)O3FeAs

K. -W. Lee

doi:10.1007/s10948-012-2066-3

paper

Effects of metallic spacer in layered superconducting Sr2(Mg $_{y}$ Ti $_{1 - y}$ )O3FeAs

arXiv:1208.2774 · doi:10.1007/s10948-012-2066-3

Abstract

The highly two-dimensional superconducting system Sr2(Mg $_{y}$ Ti $_{1 - y}$ )O3FeAs, recently synthesized in the range of 0.2 < y < 0.5, shows an Mg concentration-dependent $T_{c}$ . Reducing the Mg concentration from y=0.5 leads to a sudden increase in $T_{c}$ , with a maximum $T_{c}$ ~40 K at y=0.2. Using first principles calculations, the unsynthesized stoichiometric y=0 and the substoichiometric y=0.5 compounds have been investigated. For the 50% Mg-doped phase (y=0.5), Sr2(Mg $_{y}$ Ti $_{1 - y}$ )O3 layers are completely insulating spacers between FeAs layers, leading to the fermiology such as that found for other Fe pnictides. At y=0, representing a phase with metallic Sr2TiO3 layers, the $Γ$ -centered Fe-derived Fermi surfaces (FSs) considerably shrink or disappear. Instead, three $Γ$ -centered Ti FSs appear, and in particular two of them have similar size, like in MgB2. Interestingly, FSs have very low Fermi velocity in large fractions: the lowest being 0.6 $\times 1 0^{6}$ cm/s. Furthermore, our fixed spin moment calculations suggest the possibility of magnetic ordering, with magnetic Ti and nearly nonmagnetic Fe ions. These results indicate a crucial role of Sr2(Mg $_{y}$ Ti $_{1 - y}$ )O3 layers in this superconductivity.

7 pages; Proceedings of ICSM-2012

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Abstract

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Cited by in corpus (1)

Effects of metallic spacer in layered superconducting Sr2(Mg $_{y}$ Ti $_{1 - y}$ )O3FeAs