First-principles exploration of superconductivity in intercalated bilayer borophene phases

We explore the emergence of phonon-mediated superconductivity in bilayer borophenes by controlled intercalation with elements from the groups of alkali, alkaline-earth, and transition metals, using systematic first-principles and Eliashberg calculations. We show that the superconducting properties are primarily governed by the interplay between the out-of-plane (pz) boron states and the partially occupied in-plane (s+px,y) bonding states at the Fermi level. Our Eliashberg calculations indicate that intercalation with alkaline-earth-metal elements leads to the highest superconducting critical temperatures (Tc). Specifically, Be in δ₄, Mg in χ₃, and Ca in the kagome bilayer borophene demonstrate superior performance with Tc reaching up to 58 K. Our study therefore reveals that intercalated bilayer borophene phases are not only more resilient to chemical deterioration, but also harbor enhanced Tc values compared to their monolayer counterparts, underscoring their substantial potential for the development of boron-based two-dimensional superconductors.