Superconductivity of monolayer functionalized biphenylene with Dirac cones

Monolayer biphenylene is a new two-dimensional (2D) carbon allotrope, which has been experimentally synthesized and theoretically predicted to show superconductivity. In this work, we investigate functionalized biphenylene with the adsorption of Li. The superconducting critical temperature ( T c ) can be pushed from 0.59 K up to 3.91 K after Li adsorption. Our calculations confirm that the adsorption pushes the peak showing a high electronic density of states closer to the Fermi level, which usually leads to a larger T c . Furthermore, the application of biaxial tensile strain can soften phonons and further enhance the T c up to 15.86 K in Li-deposited biphenylene. Interestingly, a pair of type-II Dirac cones below the Fermi level has been observed, expanding the range of Dirac materials. It suggests that monolayer biphenylene deposited with Li may be a material with potential applications and improves the understanding of Dirac-type superconductors. The superconducting critical temperature T c of biphenylene can be pushed from 0.59 K to 3.91 K after Li deposition. Biaxial tensile strain can soften phonons and further increase T c up to 15.86 K at = 12% tensile strain in Li-deposited biphenylene.