Abstract A systematic density functional theory based first principles electronic structure studies on AeAFe 4 As 4 known as, 1144 iron based superconductors (IBSC) for various Ae = Ca, Sr, Eu and different alkali metals A = K, Rb, Cs are presented. Our study reveals multi-orbital derived multi-band nature of the electronic structure as well as Fermi surfaces for all the compounds. In contrast to the electronic structure of most of the Fe-based superconductors, significant contribution from As-4 p z and its mixing with Fe-3d is found at the Fermi level. A unique feature of the electronic structure of these compounds reveal orbital selective electron/hole self-doping. This is due to natural chemical pressure of larger/smaller atomic (Ae/A) sizes of various members of 1144 family. The different chemical potential (self-doping) of different orbital derived electron/hole bands causes crossing of the Fermi level for some bands, leading to orbital selective chemical pressure induced topological Lifshitz transition. This natural pressure induced orbital selective Lifshitz transition of hole bands is a unique characteristic of this family of iron based superconductors. Our conclusions remain robust even in presence of moderate electron correlation and spin-orbit coupling. Different combinations of Ae and A in different 1144 materials causes different bandwidths to different orbital selective bands; bandwidths of different bands that crosses Fermi level around Γ -point are evaluated. A large value of bandwidths for most of the compounds including EuAFe 4 As 4 indicates weak correlation effect in these compounds.

中文翻译：

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1144 Fe基超导体：轨道选择性自掺杂和化学压力诱导的Lifshitz跃迁的自然例子

摘要 系统的密度泛函理论基于对 AeAFe 4 As 4 的第一性原理电子结构研究，提出了 1144 种铁基超导体 (IBSC)，用于各种 Ae = Ca、Sr、Eu 和不同的碱金属 A = K、Rb、Cs。我们的研究揭示了所有化合物的电子结构以及费米表面的多轨道衍生多带性质。与大多数 Fe 基超导体的电子结构相比，在费米能级上发现了 As-4 pz 及其与 Fe-3d 混合的显着贡献。这些化合物的电子结构的一个独特特征揭示了轨道选择性电子/空穴自掺杂。这是由于 1144 家族不同成员的较大/较小原子 (Ae/A) 大小的自然化学压力所致。不同轨道衍生电子/空穴带的不同化学势（自掺杂）导致某些带的费米能级交叉，导致轨道选择性化学压力诱导拓扑 Lifshitz 跃迁。这种自然压力引起的空穴带轨道选择性 Lifshitz 跃迁是该铁基超导体家族的独特特征。即使存在中等电子相关性和自旋轨道耦合，我们的结论仍然是稳健的。不同1144材料中Ae和A的不同组合导致不同轨道选择带的带宽不同；评估跨越 Γ 点附近费米能级的不同频带的带宽。包括 EuAFe 4 As 4 在内的大多数化合物的带宽值较大，表明这些化合物的相关效应较弱。