Few layers of graphene at small twist angles have emerged as a fascinating platform for studying the problem of strong interactions in regimes with a nearly quenched single-particle kinetic energy and nontrivial band topology. Starting from the strong-coupling limit of twisted bilayer graphene with a vanishing single-electron bandwidth and interlayer tunneling between the same sublattice sites, we present an exact analytical theory of the Coulomb interaction-induced low-energy optical spectral weight at all integer fillings. In this limit, while the interaction-induced single-particle dispersion is finite, the optical spectral weight vanishes identically at integer fillings. We study corrections to the optical spectral weight by systematically including the effects of experimentally relevant strain-induced renormalization of the single-electron bandwidth and interlayer tunnelings between the same sublattice sites. Given the relationship between the optical spectral weight and the diamagnetic response that controls superconducting 𝑇𝑐, our results highlight the relative importance of specific parent insulating phases in enhancing the tendency towards superconductivity when doped away from integer fillings.

中文翻译：

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莫尔石墨烯中的低能量光学和规则


小扭曲角的几层石墨烯已成为研究在具有几乎猝灭的单粒子动能和非平凡能带拓扑的机构中强相互作用问题的迷人平台。从单电子带宽消失的扭曲双层石墨烯的强耦合极限和相同亚晶格位点之间的层间隧穿开始，我们提出了一个精确的解析理论，即所有整数填充物处库仑相互作用诱导的低能光谱权重。在这个极限中，虽然相互作用诱导的单粒子色散是有限的，但光谱权重在整数填充处消失得相同。我们通过系统地包括实验相关的应变诱导的单电子带宽重整化和相同亚晶格位点之间的层间隧穿的影响来研究光谱权重的校正。鉴于光谱权重和控制超导 Tc 的抗磁响应之间的关系，我们的结果强调了特定母体绝缘相在从整数填充物中掺杂时增强超导趋势中的相对重要性。