Superconductivity on the verge of electronic topological transition in Fe based superconductors

TL;DR

This study uses first principles simulations to explore electronic topological transitions in Fe-based superconductors, revealing their correlation with optimal superconductivity and magnetism disappearance, and highlighting Fermi surface sensitivity as a key probe.

Contribution

It provides a comprehensive first principles analysis of Lifshitz transitions in Fe-based superconductors, linking topological changes to superconducting and magnetic properties.

Findings

Lifshitz transitions occur at doping levels with highest superconductivity.

Transitions are associated with changes in electron and hole Fermi surfaces.

Fermi surface areas are more sensitive indicators of topological changes than band structures.

Abstract

A comprehensive first principles study on the electronic topological transition in a number of 122 family of Fe based superconductors is presented. Doping as well as temperature driven Lifshitz transitions are found from first principles simulations in a variety of Fe based superconductors that are consistent with experimental findings. In all the studied compounds the Lifshitz transitions are consistently found to occur at a doping concentration where superconductivity is highest and magnetism disappears. Systematically, the Lifshitz transition occurs in the electron Fermi surfaces for hole doping, whereas in hole Fermi surfaces for electron doping as well as iso-electronic doping. Temperature driven Lifshitz transition is found to occur in the iso-electronic Ru-doped BaFe$_2$As$_2$ compounds. Fermi surface areas are found to carry sensitivity of topological modifications more acutely than the band structures and can be used as a better experimental probe to identify electronic topological transition.