The electronic structure of the reentrant superconductor $\mathrm{Eu}({\mathrm{Fe}}_{0.86}{\mathrm{Ir}}_{0.14}$)${}_2{\mathrm{As}}_2$ ($T_c=22$ K) with coexisting ferromagnetic order ($T_M=18$ K) is investigated using angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy. We study the in-plane and out-of-plane band dispersions and Fermi surface (FS) of $\mathrm{Eu}{\left({\mathrm{Fe}}_{0.86}{\mathrm{Ir}}_{0.14}\right)}_2{\mathrm{As}}_2$. The near-$E_F$ Fe-$3d$-derived band dispersions near the $\mathrm{\Gamma }$ and $X$ high-symmetry points show changes due to Ir substitution, but the FS topology is preserved. From momentum-dependent measurements of the superconducting gap measured at $T=5$ K, we estimate an essentially isotropic $s$-wave gap ($\mathrm{\Delta }\sim 5.25\pm 0.25$ meV), indicative of strong-coupling superconductivity with $2\mathrm{\Delta }/k_B{T}_c\simeq 5.8$. The gap gets closed at temperatures $T\ge 10$ K, and this is attributed to the resistive phase which sets in at $T_M=18$ K due to the ${\mathrm{Eu}}^{2+}$-derived magnetic order. The modification of the FS with Ir substitution clearly indicates an effective hole doping with respect to the parent compound.

中文翻译：

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凹入铁磁超导体Eu（Fe0.86Ir0.14）2As2的能带结构和费米表面

折返超导体的电子结构 $\mathrm{欧洲联盟}（{铁}_{0.86}{铱}_{0.14}$）${}_{\mathrm{2个}}{\mathrm{作为}}_{\mathrm{2个}}$ （${Ť}_C=22$ K）与铁磁序共存（${Ť}_{\mathrm{中号}}=\mathrm{18岁}$使用角分辨光发射光谱法和扫描隧道光谱法研究K）。我们研究了平面内和平面外的色散和费米表面（FS）$\mathrm{欧洲联盟}{（{铁}_{0.86}{铱}_{0.14}）}_{\mathrm{2个}}{\mathrm{作为}}_{\mathrm{2个}}$。近$E_F$ 铁-$3d$导带附近的色散 $\mathrm{\Gamma }$ 和 $X$高对称点显示由于Ir取代而发生的变化，但FS拓扑得以保留。根据超导间隙的动量相关测量$Ť=5$ K，我们估计基本上是各向同性的 $s$波隙（$\mathrm{\Delta }〜5.25\pm 0.25$ meV），表明与 $\mathrm{2个}\mathrm{\Delta }/{ķ}_{乙}{Ť}_C\simeq 5.8$。间隙在温度下闭合$Ť\ge 10$ K，这归因于在 ${Ť}_{\mathrm{中号}}=\mathrm{18岁}$ K由于 ${\mathrm{欧洲联盟}}^{\mathrm{2个}+}$磁性顺序。用Ir取代对FS进行的修饰清楚地表明相对于母体化合物的有效空穴掺杂。