Crystal Chemical Concept of Arrangement and Function of Layered Superconducting Materials

TL;DR

This paper proposes a crystal chemical concept explaining the arrangement and function of layered superconducting materials, emphasizing the role of structural sandwiches in high-temperature superconductors and their influence on critical temperature (Tc).

Contribution

It introduces a new crystal chemical framework highlighting the importance of structural sandwiches over individual planes in layered superconductors.

Findings

Structural sandwiches are key to superconductivity in HTSC cuprates, diborides, and borocarbides.

Correlations between Tc and crystal parameters are similar across different classes.

Superconductivity requires channels for charge flow, carrier compression, and directional focusing.

Abstract

The crystal chemical concept of arrangement and function of layered superconducting materials is supposed. The concept is based on results of our investigation of crystal chemistry of high-temperature superconductors (HTSC) cuprates, diborides AB2 and borocarbides of nickel RNi2B2C. According to these results: (1) the main role in appearance of superconductivity played by the structural fragments - sandwiches A2(CuO2) in HTSC cuprates, A2(B2) in diborides and RB(Ni) in nickel borocarbides but not the separate planes of CuO2, B2 or Ni; (2) correlations between Tc and crystal chemical parameters of these sandwiches have similar character in all three classes of compounds, despite of distinction of a nature of their superconductivity. The central idea of the concept consists in following: in contrast to metallic conduction, for which it is enough to provide only concentration and mobility of charge carriers, for occurrence of a superconductivity it is necessary to create in addition a space (channels) for stream of charge carriers, compression of stream of carriers and focusing to direction on path of motion