Strain induced flat-band superconductivity and symmetry breaking

Superconductivity in single-layer graphene has attracted considerable interest. Here, using the determinant quantum Monte Carlo method, we study transitions of superconductivity and magnetism in a graphene monolayer with a special periodic strain. Consistent with experiments, the deformation accumulates a series of flat bands, causing a stability under interaction that is verified through electron localization in real space. During the reconstruction of the band structure, the flat-band superconductivity appears with next-nearest neighbor d+id pairing symmetry dominating other modes and is accompanied by ferromagnetism caused by symmetry breaking. We also demonstrate that the strain-induced symmetry breaking would accumulate an energy-gap antiferromagnetic insulating phase at half filling even under the limitation of not strong enough interaction, which shows its potential as a platform that exhibits strongly correlated phenomena.