Flux pinning mechanisms in graphene-doped MgB2 superconductors

The effects of graphene doping on the superconducting properties of MgB2 were studied. We found that small addition of graphene significantly improves the superconducting properties of MgB2, with only a small reduction in Tc. Low resistivity, high critical fields and enhanced flux-flow activation energy were observed for the optimally doped bulk sample. The spatial fluctuation in the transition temperature (δTc pinning) is the flux pinning mechanism in graphene-doped MgB2.