Kondo Resonance, Pomeranchuk Effect, and Heavy Fermi Liquid in Twisted Bilayer Graphene - A Numerical Renormalization Group Study

Low energy electron Hamiltonian in the magic-angle twisted bilayer graphene can be equivalently reformulated as a topological heavy fermion model [Phys. Rev. Lett. 129, 047601 (2022)]. It consists of effective localized f-electrons at AA-stacking regions and itinerant Dirac c-electrons. In this work, we applied systematic analytical and numerical renormalization group analyses to a single-impurity version of this model. We obtained a phase diagram consisting of a Fermi liquid phase in the Kondo regime, a Fermi liquid phase in the frozen impurity regime, and various local moment phases with different spin momenta. Remarkably, this single impurity phase diagram explains a series of experimental discoveries reported recently: (i) the zero-energy peak at fillings 1 ? |ν|