Chern Insulators and Topological Flat-bands in Magic-angle Twisted Bilayer Graphene

Understand

Magic-angle twisted bilayer graphene (MA-TBG) exhibits intriguing quantum phase transitions triggered by enhanced electron-electron interactions when its flat-bands are partially filled.

• However, the phases themselves and their connection to the putative non-trivial topology of the flat bands are largely unexplored.
• Here we report transport measurements revealing a succession of doping-induced Lifshitz transitions that are accompanied by van Hove singularities (VHS) which facilitate the emergence of correlation-induced gaps and topologically non-trivial sub-bands.
• In the presence of a magnetic field, well quantized Hall plateaus at filling of 1, 2, 3 carriers per moir\'e-cell reveal the sub-band topology and signal the emergence of Chern insulators with Chern-numbers, ! = !, !, !, respectively.