Recently, superconductivity was discovered at very low densities in slightly misaligned graphene multilayers. Surprisingly, despite extremely low electronic density (about $10^{-4}$ electrons per unit cell), these systems realize strong-coupling superconductivity, with the transition temperature being a large fraction of the Fermi energy ($T_c\sim 0.1 \epsilon_F$). Here we propose a qualitative explanation for this remarkable phenomenon, highlighting similarities and qualitative differences with the conventional uniform high-density superconductivity. Most importantly, we find that periodic superimposed potential generically enhances local interactions relative to nonlocal (for instance, Coulomb) interactions. In addition, the density of states is enhanced as well, exponentially in modulation strength for low lying bands in some cases. Combination of these two effects makes moir\'e systems natural intermediate or strong-coupled superconductors, with potential for very high transition temperatures.

中文翻译：

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莫尔超导

最近，在轻微错位的石墨烯多层膜中发现了密度非常低的超导性。令人惊讶的是，尽管电子密度极低（每个晶胞约 $10^{-4}$ 电子），但这些系统实现了强耦合超导性，转变温度是费米能量的很大一部分（$T_c\sim 0.1 \epsilon_F $）。在这里，我们提出了对这种显着现象的定性解释，突出了与传统均匀高密度超导的相似之处和定性差异。最重要的是，我们发现周期性叠加势相对于非局部（例如库仑）相互作用一般会增强局部相互作用。此外，状态密度也得到增强，在某些情况下，低频段的调制强度呈指数增长。