Multigap superconductivity in lithium intercalated bilayer Mo₂C

Interlayer coupling can significantly influence the physical properties of layered transition metal compounds. The superconductivity in layered Mo₂C systems, belonging to the emergent family of MXene, has garnered considerable attention. However, the impact of interlayer coupling on superconductivity, and the anisotropic superconducting properties in these systems are not yet clear. By performing first-principles calculations of electron-phonon coupling and anisotropic superconducting properties, we show that the interlayer coupling in bilayer 1T-Mo₂C suppresses superconductivity, resulting in a significant drop in superconducting transition temperature (Tc) from 4.2 K in its monolayer form to nearly 0 K. By introducing lithium atoms into the interlayer space of the bilayer, the interlayer coupling can be effectively weakened, transforming the system into a two-gap superconductor with a Tc above 10 K. A 3% tensile strain can further transform the system into a three-gap superconductor with a significantly enhanced Tc of approximately 24.7 K, which is very high in the Mo₂C related systems. The enhancement of the superconductivity induced by the strain is mainly due to the downshift of an energy band with a flat dispersion to the energy near the Fermi level. The in-plane vibrations of Mo atoms and the d-orbital electrons of Mo atoms are most important for the formation of the superconductivity. Our method can also be applied to multilayer Mo₂C systems. Given the successful synthesis of layered Mo₂C systems and the experimental realization of alkaline metal atom depositions, our work presents a practically feasible strategy for achieving high Tc and multigap superconductivity in layered Mo₂C.