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# Magic-angle Twisted Bilayer Systems with Quadratic-Band-Touching: Exactly Flat Bands with High-Chern Number

Cornell University - arXiv
Nov 2021

Studies of twisted morie systems have been mainly focused on 2D materials like graphene with Dirac points and transition-metal-dichalcogenide so far. Here we propose a new twisted bilayer of 2D systems which feature quadratic-band-touching points and find exotic physics different from previously studied twisted morie systems. Specifically, we show that exactly flat bands can emerge at magic angles and, more interestingly, each flat band exhibits a high Chern number ($C=\pm 2$) which was not realized in bilayer morie systems before. We further consider the effect of Coulomb interactions in such magic-angle twisted system and find that the ground state supports the quantum anomalous Hall effect with quantized Hall conductivity $2\frac{e^2}{hc}$ at certain filling. Furthermore, possible physical realization of such twisted bilayer systems will be briefly discussed.

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