The discovery of different phases as a result of correlations, especially in low-dimensional materials, has been always an exciting and fundamental subject of research. Recent experiments on twisted bilayer graphene… Click to show full abstract
The discovery of different phases as a result of correlations, especially in low-dimensional materials, has been always an exciting and fundamental subject of research. Recent experiments on twisted bilayer graphene have revealed reentrant unconventional superconductivity as a function of doping as well as a Mott-like insulating phase when the two layers are twisted with respect to each other at certain ``magic'' angles for doping, corresponding to two particles per moir\'e unit cell. In this paper, we propose a microscopic model that takes into account interactions and the Van Hove singularities in the density of states of twisted bilayer graphene at doping corresponding to one particle ($\ensuremath{\nu}=1$) per moir\'e unit cell and study how superconductivity emerges. We identify the possible symmetry of the order parameter as ${s}^{\ifmmode\pm\else\textpm\fi{}}$, while, if the intervalley coupling is negligible, the symmetry is ${s}^{++}$. In addition, we find and characterize the insulating region of the system as a region with a uniform charge instability where there is coexistence of the metallic and insulating phases.
               
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