Phonon-mediated superconductivity in two-dimensional hydrogenated phosphorus carbide: HPC3.

In recent years, three-dimensional (3D) high-temperature superconductors at ultrahigh pressure have been reported, typical examples are the polyhydrides H3S, LaH10, YH9, etc. To find high-temperature two-dimensional (2D) superconductors at atmospheric pressure is another research hotspot. Here, we investigated the possible superconductivity in a hydrogenated monolayer phosphorus carbide based on first-principles calculations. The results reveal that monolayer PC3 transforms from a semiconductor to a metal after hydrogenation. Interestingly, the C-π-bonding band contributes most to the states at the Fermi level. Based on the electron-phonon coupling mechanism, it is found that the electron-phonon coupling constant of HPC3 is 0.95, which mainly originates from the coupling of C-π electrons with the in-plane vibration modes of C and H. The calculated critical temperature Tc is 31.0 K, which is higher than those in most 2D superconductors. By further applying a biaxial tensile strain of 3%, the Tc can be boosted to 57.3 K, exceeding the McMillan limit. Thus, hydrogenation and strain are effective ways for increasing the superconducting Tc of 2D materials.