The bulk electronic structures of two high-order quaternary approximants of F-type icosahedral ($i$)-Al-Pd-TM quasicrystal: Al-Pd-Cr-Fe and Al-Pd-Mo-Fe, having similar electron to atom ($e/a$) ratio as $i$-Al-Pd-Mn quasicrystal, have been investigated by hard x-ray photoelectron spectroscopy. We establish the presence of a well-formed pseudogap at the Fermi level in both the approximants. The pseudogap turns out to be deeper in the approximants compared to $i\text{−}\mathrm{Al}\text{−}\mathrm{Pd}\text{−}\mathrm{Mn}$, and this is supported by specific heat data. Modifications in the line shape of Al $2s$ core-level main peak as well as the plasmon loss peaks indicate enhanced hybridization of Al $sp$ and transition metal $d$ states in the approximants, which could be one of the possible reasons for their pseudogap. The absence of magnetic exchange splitting in the Fe $2p$ core-level spectra establishes the nonmagnetic nature of the approximants.

中文翻译：

---

高阶四元近似的体电子结构

F型二十面体的两个高阶四元近似的体电子结构（$\mathrm{一世}$）-Al-Pd-TM准晶体：Al-Pd-Cr-Fe和Al-Pd-Mo-Fe，具有与原子相似的电子（$Ë/\mathrm{一种}$）比率为 $\mathrm{一世}$-Al-Pd-Mn准晶体已通过硬X射线光电子能谱进行了研究。我们在两个近似值中都建立了一个在费米能级上格式良好的伪间隙。伪间隙在近似值中比$\mathrm{一世}\text{-}铝\text{-}钯\text{-}锰$，这由特定的热量数据支持。Al的线形变形$2s$ 核心水平的主峰以及等离激元损失峰表明Al的杂交增强 $sp$ 和过渡金属 $d$近似中的状态，这可能是其伪间隙的可能原因之一。铁中没有磁交换分裂$2p$ 核心层谱建立了近似值的非磁性性质。