Moiré systems displaying flat bands have emerged as novel platforms to study correlated electron phenomena. Insulating and superconducting states appear upon doping magic angle twisted bilayer graphene (TBG), and there is evidence of correlation induced effects at the charge neutrality point (CNP) which could originate from spontaneous symmetry breaking. Our theoretical calculations show how optical conductivity measurements can distinguish different symmetry breaking states, and reveal the nature of the correlated states. In the specific case of nematic order, which breaks the discrete rotational symmetry of the lattice, we find that the Dirac cones are displaced, not only in momentum space but also in energy, inducing finite Drude weight at the CNP. We also show that the sign of the Drude weight anisotropy induced by a nematic order depends on the degree of lattice relaxation, the doping and the nature of the symmetry breaking.

显示平坦带的莫尔条纹系统已经成为研究相关电子现象的新颖平台。在掺杂魔角扭曲双层石墨烯（TBG）时会出现绝缘和超导状态，并且有证据表明在电荷中性点（CNP）上相关诱导的效应可能源自自发对称性破坏。我们的理论计算表明，光导率测量如何区分不同的对称断裂状态，并揭示相关状态的性质。在破坏列阵离散旋转对称性的向列顺序的特定情况下，我们发现狄拉克锥不仅在动量空间而且在能量上均发生位移，从而在CNP处感应出有限的Drude权重。