Surface-chemistry-engineered strong-coupling superconductivity in halogen-functionalized Mo₂C MXenes

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Materials

Background:

• Two-dimensional (2D) MXenes offer a tunable platform for exploring quantum phenomena.
• Surface chemistry is crucial for engineering emergent quantum phases in MXenes.

Purpose of the Study:

• To investigate the potential of halogen functionalization for inducing strong-coupling superconductivity in Mo2C MXene monolayers.
• To explore the effects of electron doping and strain on superconductivity in these functionalized materials.

Main Methods:

• First-principles calculations were employed to study halogen-functionalized Mo2C monolayers.
• Analysis included dynamical and mechanical stability, electronic structure, and electron-phonon coupling (EPC) using Eliashberg spectral functions.
• The Allen-Dynes formalism was used to calculate superconducting transition temperatures.

Main Results:

• Br- and I-functionalized Mo2C monolayers were found to be dynamically and mechanically stable.
• Enhanced density of states near the Fermi level and strong EPC were observed, particularly from Mo-dominated phonon modes.
• Calculated superconducting transition temperatures reached 13.1 K for Mo2CBr2 and 18.1 K for Mo2CI2.
• Electron doping increased coupling strength, raising the transition temperature above 27.5 K, while strain showed competing effects.

Conclusions:

• Halogen functionalization is a viable strategy for achieving strong-coupling superconductivity in Mo2C MXenes.
• Surface chemistry and external stimuli like doping and strain offer pathways for tuning superconductivity in 2D materials.