We propose a generalized model of electronic structure modification in HTSC cuprates and ferropnictides under doping. In this model, the role of doping consists in only a local change in the electronic structures of the parent phases of cuprates and ferropnictides due to the formation of trion complexes comprising a doped carrier localized in unit cell and charge transfer (CT) excitons around it. These CT excitons emerge in CuO₄ or AsFe₄ plaquettes in the CuO₂ or FeAs basal planes (CT plaquettes) under the influence of the doped carrier, restricting its itinerancy. As the dopant concentration is increased, CT plaquettes combine into clusters of the so-called CT phase. It is this CT phase that is related in the model to the HTSC phase. In support of this assumption, we determined the ranges of dopant concentrations conforming to the existence of percolation clusters of the CT phase; these ranges were shown to coincide with the positions of the superconducting domes on the phase diagrams of these compounds. The model also perfectly describes subtle features of the phase diagrams of various cuprates and ferropnictides including the “1/8” anomaly, narrow peaks in the dependences of the London penetration depth on the concentration of the dopant, and other specific features. The mechanism of the generation of free carriers in the CT phase, provided by intrinsic self-doping, was considered. The mechanism is not directly related to external doping, but is due to the interaction of band electrons with so-called Heitler–London (HL) centres inherently existing in the percolation cluster of the CT phase and representing pairs of adjacent CuO₄ or AsFe₄ CT plaquettes in the CuO₂ or FeAs basal planes. Material in the CT phase was shown to represent a medium, in which the mechanism of excitonic superconductivity, specified by the interaction of band electrons with HL centres, can be realized.

中文翻译：

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HTSC铜酸盐和亚铁氰化物的掺杂机理和相图特征。

我们提出了在掺杂下HTSC铜酸盐和亚铁氰化物中电子结构修饰的通用模型。在该模型中，掺杂的作用仅在于铜盐和亚铁氰化物的母体相的电子结构中的局部变化，这是由于三元复合物的形成，其中三元复合物包含位于晶胞中的掺杂载流子及其周围的电荷转移（CT）激子。这些CT激子以CuO出现₄或ASFE _4个plaquettes在的CuO ₂或FeAs基底平面（CT碎片）受掺杂载体的影响，限制了其迭代。随着掺杂剂浓度的增加，CT球团结合成所谓的CT相簇。该CT阶段与模型中的HTSC阶段相关。为了支持这一假设，我们确定了符合CT相渗滤团簇存在的掺杂剂浓度范围。这些范围显示出与这些化合物的相图上的超导圆顶的位置一致。该模型还完美地描述了各种铜酸盐和亚铁氰化物的相图的细微特征，包括“ 1/8”异常，伦敦穿透深度对掺杂剂浓度的依赖性上的窄峰以及其他特定特征。考虑了由固有自掺杂提供的CT相中自由载流子产生的机理。该机制与外部掺杂并不直接相关，而是由于带电子与CT相的渗流簇中固有存在的所谓Heitler-London（HL）中心相互作用，并表示成对的相邻CuOCuO ₂或FeAs基面中的₄或AsFe ₄ CT球团。显示出CT相中的材料代表一种介质，其中可以实现由带电子与HL中心的相互作用所指定的激子超导机理。