Local transformation of the Electronic Structure and Generation of Free Carriers in Cuprates and Ferropnictides under Heterovalent and Isovalent Doping

TL;DR

This paper presents a unified model explaining how heterovalent and isovalent doping transform the electronic structure of cuprates and ferropnictides, leading to free carrier generation and superconductivity, based on self-localization of doped carriers.

Contribution

It introduces a novel unified framework for understanding electronic structure changes in doped cuprates and ferropnictides, emphasizing self-localization and cluster formation.

Findings

Doped carriers form percolation clusters with a self-doped excitonic insulator structure.

The model predicts the sign of generated free carriers, which may differ from the doped carriers.

A mechanism for free carrier generation under various doping types is proposed.

Abstract

We have previously shown that most of the anomalies in the superconducting characteristics of cuprates and ferropnictides observed at dopant concentrations within the superconducting dome, as well as the position of the domes in the phase diagrams, do not require knowledge of the details of their electronic structure for explanation, but can be understood and calculated with high accuracy within the framework of a simple model describing the cluster structure of the superconducting phase. This fact suggests a change in the paradigm that forms our understanding of HTSC. In this paper, we propose a unified view on the transformation of the electronic structure of cuprates and ferropnictides upon heterovalent and isovalent doping, based on the assumption of self-localization of doped carriers. In this representation, in undoped cuprates and ferropnictides, which initially have different electronic structures (Mott insulator and semimetal), local doping forms percolation clusters with the same electronic structure of a self-doped excitonic insulator where a specific mechanism of superconducting pairing is implemented, which is genetically inherent in such a system. The proposed model includes a mechanism for generating additional free carriers under heterovalent and isovalent doping and makes it possible to predict their sign, which, in the general case, does not coincide with the sign of doped carriers.