First-principles Electronic Structure of Superconductor   Ca$_4$Al$_2$O$_6$Fe$_2$P$_2$: Comparison with LaFePO and   Ca$_4$Al$_2$O$_6$Fe$_2$As$_2$

Taichi Kosugi; Takashi Miyake; Shoji Ishibashi

arXiv:1109.2054·cond-mat.supr-con·May 30, 2015

First-principles Electronic Structure of Superconductor Ca$_4$Al$_2$O$_6$Fe$_2$P$_2$: Comparison with LaFePO and Ca$_4$Al$_2$O$_6$Fe$_2$As$_2$

Taichi Kosugi, Takashi Miyake, Shoji Ishibashi

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TL;DR

This study uses first-principles calculations to analyze the electronic structures of Ca4Al2O6Fe2Pn2 superconductors, revealing how pnictogen height influences Fermi surface topology and discussing implications for superconductivity.

Contribution

It provides a detailed comparison of electronic structures among Ca4Al2O6Fe2Pn2 compounds and elucidates the effect of pnictogen height and alloying on their electronic properties.

Findings

01

Ca4Al2O6Fe2P2 has multiple Fermi surfaces around Γ and M.

02

Differences in band structures mainly stem from pnictogen height.

03

Alloying Ca4Al2O6Fe2As with P results in electronic structures similar to pure compounds.

Abstract

We investigate the electronic structures of iron-based superconductors having perovskite-like blocking layers, %Ca $_{4}$ Al $_{2}$ O $_{6}$ Fe $_{2}$ (As $_{1 - x}$ P $_{x}$ ) $_{2}$ from first principles. Ca $_{4}$ Al $_{2}$ O $_{6}$ Fe $_{2}$ P $_{2}$ and Ca $_{4}$ Al $_{2}$ O $_{6}$ Fe $_{2}$ As $_{2}$ from first principles. Ca $_{4}$ Al $_{2}$ O $_{6}$ Fe $_{2}$ P $_{2}$ is found to have two hole-like Fermi surfaces around $Γ$ , and one hole-like Fermi surface around M in the unfolded Brillouin zone. This is in contrast with LaFePO, where no Fermi surface is found around M. The relationship of their band structures and measured transition temperatures of superconductivity is discussed. The number of Fermi surfaces in Ca $_{4}$ Al $_{2}$ O $_{6}$ Fe $_{2}$ P $_{2}$ is also different from that of Ca $_{4}$ Al $_{2}$ O $_{6}$ Fe $_{2}$ As $_{2}$ , in which only one Fermi surface is formed around $Γ$ . Analysis using maximally localized Wannier functions clarifies that the differences between their…

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