Enhanced Superconductivity in Lithium-Sandwiched Graphene

Two-dimensional (2D) materials exhibiting strong electron–phonon coupling provide a powerful platform for investigating superconductivity in reduced dimensions. In this work, we present a systematic first-principles study of phonon-mediated superconductivity in a lithium-sandwiched graphene heterostructure. Density-functional theory (DFT) is combined with Wannier-function-based interpolation of electron–phonon matrix elements to ensure highly converged and accurate descriptions of the coupling. The superconducting properties are obtained by solving the fully anisotropic Eliashberg equations for a representative Coulomb pseudopotential of μ* = 0.14, yielding a superconducting transition temperature T c ≈ 70 K, driven by a strong electron–phonon coupling constant λ ≈ 1.7. A detailed analysis reveals that low-frequency phonon modes associated with the intercalated lithium layers dominate the coupling, exhibiting strong hybridization with graphene π states at the Fermi level. These results demonstrate that lithium intercalation introduces low-frequency Li-related vibrational modes that strongly interact with the electronic states near the Fermi level, thereby significantly enhancing the electron–phonon coupling strength.