Superconductivity in Ca-intercalated bilayer graphene: C₂CaC₂.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Superconductivity in graphene is induced by metal atom deposition or intercalation.
• Existing metal-intercalated graphenes show relatively low critical temperatures (Tc).
• Higher Tc superconductors are sought for advanced technological applications.

Purpose of the Study:

• To predict and investigate a new Ca-intercalated bilayer graphene (C2CaC2) with potentially higher superconductivity.
• To explore the electronic structure, electron-phonon coupling (EPC), and superconducting properties of C2CaC2.
• To assess the impact of strain on the superconducting properties of C2CaC2.

Main Methods:

• First-principles calculations were employed to study C2CaC2.
• Thermodynamic and dynamic stability of C2CaC2 were assessed.
• Electronic structure, EPC, and superconducting properties were calculated.

Main Results:

• C2CaC2 was predicted to be thermodynamically and dynamically stable.
• The electron-phonon coupling in C2CaC2 primarily involves C-p orbitals and C atom vibrations.
• A superconducting critical temperature (Tc) of 18.9 K was calculated for C2CaC2.
• Applying -4% biaxial compressive strain boosted the Tc to 26.6 K.

Conclusions:

• C2CaC2 exhibits significantly higher superconductivity than previously reported metal-intercalated bilayer graphenes.
• The high Tc in C2CaC2 is attributed to strong electron-phonon coupling.
• C2CaC2 represents a promising new material for achieving high-Tc superconductivity in bilayer graphene systems.