Strain-induced interstitial anionic electrons and superconductivity of monolayer BaCu

Abstract Recently, a novel electride, BaCu, which contains no light elements, has been both predicted and synthesized. This material adds to the list of inorganic two-dimensional (2D) interlayer electrides, including Ca2N and Y2C. However, the electride properties of the BaCu monolayer are not known, and its characteristics have not been thoroughly investigated. Here, our first-principles calculations indicated that the BaCu monolayer is a weak electride with few interstitial anionic electrons (IAEs). Notably, biaxial tensile strain can significantly alter the electronic properties of the BaCu monolayer, leading to the increase of IAEs. This strain causes a redistribution of charge from the Ba and Cu atoms to the IAEs. Additionally, the biaxial tensile strain induces superconductivity in the BaCu monolayer, and a notable increase in the critical superconducting transition temperature (Tc) to 0.2 K at 10% strain is observed. The coupling between the vibrations of the Cu atoms and IAEs plays a crucial role in this superconductivity. Our findings provide valuable insights into the relationship between the IAEs and superconductivity in the 2D electrides.