Heavy quasiparticles and cascades without symmetry breaking in twisted bilayer graphene

Among the variety of correlated states exhibited by twisted bilayer graphene, cascades in the spectroscopic properties and in the electronic compressibility occur over larger ranges of energy, twist angle and temperature compared to other effects. This suggests a hierarchy of phenomena. Using a combined dynamical mean-field theory and Hartree calculation, we show that the spectral weight reorganisation associated with the formation of local moments and heavy quasiparticles can explain the cascade of electronic resets without invoking symmetry breaking orders. The phenomena reproduced here include the cascade flow of spectral weight, the oscillations of remote band energies, and the asymmetric jumps of the inverse compressibility. We also predict a strong momentum differentiation in the incoherent spectral weight associated with the fragile topology of twisted bilayer graphene. Twisted bilayer graphene hosts a sequence of electronic resets evidenced experimentally by characteristic spectroscopic cascades and sawtooth peaks in the inverse electronic compressibility. Here, the authors use combined dynamical mean-field theory and Hartree calculations to demonstrate that symmetry-breaking transitions are not necessary to observe cascades in twisted bilayer graphene.