Correlated states in magic angle twisted bilayer graphene under the optical conductivity scrutiny

Moiré systems displaying flat bands have emerged as novel platforms to study correlated electron physics. There is evidence of correlation induced effects at the charge neutrality point (CNP) of twisted bilayer graphene which could originate from spontaneous symmetry breaking. We will show how optical conductivity measurements allow to distinguish different symmetry breaking states and to follow the evolution of the band distortions with doping. In the specific case of a nematic order, which breaks the discrete rotational symmetry of the lattice, we find that the Dirac cones tend to be displaced, not only in momentum space but also in energy, inducing a finite density of states and Drude weight at the CNP. The nematic order is revealed in a dc conductivity anisotropy with its sign depending on the degree of relaxation, the doping and the nature of the symmetry breaking