Maximizing Fermi surface multiplicity optimizes superconductivity in iron pnictides

TL;DR

This paper investigates how the lattice structure, especially the Fe-As-Fe bond angle, influences superconductivity in iron pnictides, revealing that optimal superconductivity occurs when the arsenic atoms form a regular tetrahedron with maximized hole Fermi surface multiplicity.

Contribution

It identifies the specific lattice geometry that maximizes Fermi surface multiplicity and correlates it with optimal superconductivity in iron pnictides.

Findings

Maximum hole Fermi surface multiplicity occurs near the regular tetrahedron bond angle.

Superconductivity is optimized within the three hole Fermi surface regime.

Antiferromagnetic Stoner factor tends to increase as the bond angle decreases.

Abstract

We study the condition for optimizing superconductivity in the iron pnictides from the lattice structure point of view. Studying the band structure of the hypothetical lattice structure of LaFeAsO, the hole Fermi surface multiplicity is found to be maximized around the Fe-As-Fe bond angle regime where the arsenic atoms form a regular tetrahedron. Superconductivity is optimized within this three hole Fermi surface regime, while the stoner factor of the antiferromagnetism has an overall tendency of increasing upon decreasing the bond angle. Combining also the effect of the varying the Fe-As bond length, we provide a guiding principle for obtaining high $T_c$.