Emergence of superconductivity in an InSe monolayer: Roles of deposited metal and biaxial strain

Two-dimensional (2D) superconductors are important for both fundamental superconducting physics and potential nanoscale applications. Here, using first-principles calculations, we unravel that an Na-deposited InSe monolayer (NaIn 2 Se 2 ) is dynamically stable and may constitute a novel 2D superconductor with a transition temperature (T c ) of 4.42 K due to the combined effect of strong Fermi nesting and strong electron-phonon coupling (EPC) from in-plane phonons. In contrast, Li- and Mg-deposited InSe monolayers are dynamically unstable. Furthermore, a 3% biaxial tensile strain increases the EPC strength of NaIn 2 Se 2 and T c is increased to 4.88 K. However, a 3% compressive strain slightly lowers T c to 4.12 K. Our work demonstrates that Na-deposited InSe monolayer may be a novel 2D superconductor and that strain is important to maximize its T c . • Na deposited InSe monolayer (NaIn 2 Se 2 ) is dynamically stable and can be a novel 2D superconductor with transition temperature of 4.42 K. • Li and Mg deposited InSe monolayer are dynamically unstable. • 3% biaxial tensile strain increases the EPC strength of NaIn 2 Se 2 and T c rises to 4.88 K.