Tuning the flat band with in-plane biaxial strain and the emergence of superconductivity in Ni3Sn

We study the electronic band structures and topological properties of nonmagnetic kagome metal $\mathrm{N}{\mathrm{i}}_{3}\mathrm{Sn}$ when applying in-plane biaxial strains through first-principles calculations. From these calculations, we confirm that the flat band of $\mathrm{N}{\mathrm{i}}_{3}\mathrm{Sn}$ is located at 250 meV below the Fermi level for pristine $\mathrm{N}{\mathrm{i}}_{3}\mathrm{Sn}$, and its position can be raised to the Fermi level by applying a finite in-plane biaxial strain. In this deformation process, we also find that there are two distinct topological phase transitions between trivial and nontrivial topological states at 1.5% and 2.9% strains. Finally, through the calculations of electron-phonon coupling, we examine the possibility of superconductivity mediated by electron-phonon coupling for pristine and strained $\mathrm{N}{\mathrm{i}}_{3}\mathrm{Sn}$ structures and confirm theoretically that the 5% biaxial strained $\mathrm{N}{\mathrm{i}}_{3}\mathrm{Sn}$ shows superconductivity. Therefore, biaxial strain in kagome metal $\mathrm{N}{\mathrm{i}}_{3}\mathrm{Sn}$ triggers the flat band to move toward the Fermi level, thereby inducing nontrivial topology and superconductivity simultaneously.