Kondo Lattice Approach for Magic-Angle Twisted Bilayer Graphene

Magic-angle twisted bilayer graphene (MATBG) has emerged as a tunable platform for low temperature correlation driven phases. Experiments have observed seemingly contrasting characteristics: delocalized electrons and localized quantum-dot behavior. Song and Bernevig have recently been able to capture both aspects by exactly mapping the Bistrizer—MacDonald model into a topological heavy fermion model with a simple real space picture. The topological heavy fermion model for MATBG opens the door for heavy-fermion machinery to be applied. Hence, starting from the topological heavy fermion model, we obtain and investigate the low energy Kondo Lattice model for MATBG. Harnessing the theoretical tools of the heavy fermion community, we solve the model using mean-field theory and explore the low-energy phases. In particular, we will show how the local moment formation mechanism is altered by the relativistic dispersion of the topological conduction electrons, resulting in modified strong coupling limits for the Kondo Lattice. We investigate the observable consequences of local moment and Kondo physics in MATBG. We finish by exploring further analogies between known phases heavy fermion materials and the diverse phase diagram of MATBG.