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 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 27 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.
The study investigates a special kind of superconductivity in bilayer borophenes—materials made of two layers of boron atoms. Superconductivity is a phenomenon where a material can conduct electricity without any resistance, usually at very low temperatures. The researchers examined how inserting different metal elements (from groups like alkali, alkaline-earth, and transition metals) between the layers of borophene affects its superconductivity. This process is known as intercalation. They used advanced calculations to understand this process, focusing on how the electrons in boron atoms interact with each other and contribute to superconductivity.
Their findings suggest that when certain alkaline-earth metals are inserted between the borophene layers, the material reaches higher critical temperatures (Tc) for superconductivity. Critical temperature is the temperature below which a material becomes superconductive. Specifically, they found that beryllium (Be) in one type of borophene structure, magnesium (Mg) in another, and calcium (Ca) in a third type showed the best performance, with Tc values reaching up to 27 Kelvin (which is very cold, about -246.15°C).
The study concludes that these intercalated bilayer borophenes are not only more stable against chemical damage but also have better superconducting properties than single-layer borophene. This points to significant potential for using boron-based two-dimensional materials in creating superconductors, which could be applied in various technologies, including medical imaging, magnetic levitation, and energy-efficient power transmission.
