Graphene Micro-Substrate Induced High Electron-Phonon Coupling in $\hbox{MgB}_{2}$

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
.