Tuning tetrahedral structure and electronic properties of FeSe films through strain engineering

Abstract We demonstrate that the magnetic, tetrahedral structure, and electronic properties of FeSe films are closely related to the in-plane biaxial strain. Our calculations show that the magnetic ground state of FeSe films maintain their striped antiferromagnetic order even under biaxial compressive or tensile strain. Upon increasing the compressive strain, the structure of the FeSe4 tetrahedron is distorted along the c-axis and deviates greatly from the ideal tetrahedron structure due to the variation in the bond angle and bond length. These variations lead to the increased hybridization of the Fe-3d and Se-4p states, greater nesting between the electron and hole bands, and more electronic states near the Fermi level. The applied compressive strain can suppress the antiferromagnetism of the system and results in an enhancement of the superconductivity of FeSe films. Conversely, the band structure and electronic properties of the system under tensile strain show opposite changes and tend to suppress the superconductivity of FeSe films. These results indicate that tuning the strain may be an effective way to control the superconducting properties of FeSe films.