Strain effects on electronic structure of the iron selenide superconductor

TL;DR

This study investigates how different types of strain affect the electronic structure and superconductivity of FeSe, revealing that c-axis strain enhances superconductivity by improving Fermi surface nesting, while tensile strain destroys it.

Contribution

It provides ab initio insights into how strain modifies Fermi surface nesting and superconductivity in FeSe, linking theoretical predictions with experimental observations.

Findings

c-axis strain improves Fermi surface nesting and enhances superconductivity

tensile strain destroys nesting and suppresses superconductivity

compressive in-plane strain slightly weakens nesting

Abstract

The influence of various strains on crystal and electronic structures of superconducting FeSe has been studied ab initio. We consider changes in the Fermi surface nesting with a vector Q=(0.5,0.5)*(2\pi /a) as crucial for rising superconductivity (SC) mediated by spin-fluctuations (SF). Our results indicate that the c-axis strained FeSe exhibits the most imperfect nesting, which enhances SF and, hence, also SC. In turn, the ab-plane compressive strain slightly weakens this} nesting while the tensile strain destroys it completely. These findings are consistent with reported earlier experimental dependencies of superconducting transition temperatures on strain in FeSe thin films.