Kinetic frustration and the nature of the magnetic and paramagnetic states in iron pnictides and iron chalcogenides

TL;DR

This study provides a comprehensive theoretical analysis of iron-based superconductors, explaining their magnetic and electronic properties and how structural variations influence superconductivity, aligning well with experimental data.

Contribution

It offers a unified theoretical framework that accurately describes magnetic and paramagnetic states across various iron compounds, linking structural parameters to electronic properties.

Findings

Consistent description of magnetic moments and effective masses across compounds

Variation in properties linked to structural parameters, not Coulomb screening

Explanation of Fermi surface dependence of superconducting gaps

Abstract

The iron pnictide and chalcogenide compounds are a subject of intensive investigations due to their high temperature superconductivity.\cite{a-LaFeAsO} They all share the same structure, but there is significant variation in their physical properties, such as magnetic ordered moments, effective masses, superconducting gaps and T$_c$. Many theoretical techniques have been applied to individual compounds but no consistent description of the trends is available \cite{np-review}. We carry out a comparative theoretical study of a large number of iron-based compounds in both their magnetic and paramagnetic states. We show that the nature of both states is well described by our method and the trends in all the calculated physical properties such as the ordered moments, effective masses and Fermi surfaces are in good agreement with experiments across the compounds. The variation of these properties can be traced to variations in the key structural parameters, rather than changes in the screening of the Coulomb interactions. Our results provide a natural explanation of the strongly Fermi surface dependent superconducting gaps observed in experiments\cite{Ding}. We propose a specific optimization of the crystal structure to look for higher T$_c$ superconductors.