Graphene Micro-Substrate Induced High Electron-Phonon Coupling in MgB₂

Electron-phonon coupling strength was studied in graphene-MgB 2 composites to explore the possibilities for a higher superconducting transition temperature ( T c ). For the first time in the experimental work on MgB 2 , the Raman active E 2g mode was split into two parts: a softened mode corresponding to tensile strain and a hardened mode attributed to the carbon substitution effect. The tensile strain effect is suggested to improve T c of graphene-MgB 2 composites because it increases the electron-phonon coupling strength of MgB 2 .