Spin/Valley Flavor Symmetry Breaking in Magic Angle Twisted Bilayer Graphene*

The spin/valley flavor symmetry of the nearly flat low-energy bands in magic angle twisted bilayer graphene (MAtBG) is often seen experimentally to be broken at partial band fillings. The pattern of flavor symmetry breaking is quite distinct from what one would expect when the flat bands are completely dispersionless, different for example from what occurs at partial filling of the N=0 Landau levels in Bernal-stacked bilayer graphene. We analyze how details of the flat band dispersion influence the flavor symmetry breaking revealed by weak-field-Hall and Shubnikov-de Haas magneto-transport measurements [1]. Additionally, we study the unique thermodynamic characteristics of the flavor symmetry breaking transition observed in recent compressibility and entropy measurements.

[1] Ming Xie and Allan H. MacDonald, arXiv:2010.07928