# Superhard and Superconducting Bilayer Borophene

## TL;DR

This paper explores a new form of borophene that is both superhard and superconducting, with potential for high-temperature superconductivity under strain.

## Contribution

The study reveals that bilayer-δ6 borophene has the highest superconducting critical temperature among borophenes and 2D materials.

## Key findings

- Bilayer-δ6 borophene has a 2D-Young’s modulus of ~570 N/m, indicating strong mechanical properties.
- The material exhibits superconductivity with a critical temperature of ~20 K.
- Applying strain can increase the critical temperature to ~46 K, the highest known for borophene or 2D elemental materials.

## Abstract

Two-dimensional superconductors, especially the covalent metals such as borophene, have received significant attention due to their new fundamental physics, as well as potential applications. Furthermore, the bilayer borophene has recently ignited interest due to its high stability and versatile properties. Here, the mechanical and superconducting properties of bilayer-δ6 borophene are explored by means of first-principles computations and anisotropic Migdal–Eliashberg analytics. We find that the coexistence of strong covalent bonds and delocalized metallic bonds endows this structure with remarkable mechanical properties (maximum 2D-Young’s modulus of ~570 N/m) and superconductivity with a critical temperature of ~20 K. Moreover, the superconducting critical temperature of this structure can be further boosted to ~46 K by applied strain, which is the highest value known among all borophenes or two-dimensional elemental materials.