Magic-angle twisted symmetric trilayer graphene as a topological heavy-fermion problem

A topological heavy-fermion (THF) model is formulated for magical-angle twisted symmetric trilayer graphene (MATSTG), where ``symmetric'' means that the top and bottom layers are rotated equally with respect to middle layer. In addition localized $f$ modes itinerant $c$ (which serve as basis of THF bilayer graphene), MATSTG consists extra Dirac ($d$) modes. The newly proposed $f\ensuremath{-}c\ensuremath{-}d$ can well reproduce previous numerical results on correlated phases at integer fillings, provide a new analytical understanding them charge neutrality.