Magic angles in twisted bilayer graphene near commensuration: Towards a hypermagic regime

Article

关键词: CORRELATED STATES;    MOIRE BANDS;    INSULATOR;    SUPERCONDUCTIVITY;    FERROMAGNETISM;    MOTT;   

DOI  :  10.1103/PhysRevB.106.115418

来源: SCIE

【 摘 要 】

The Bistritzer-MacDonald continuum model (BM model) describes the low-energy moire bands for twisted bilayer graphene (TBG) at small twist angles. We derive a generalized continuum model for TBG near any commensurate twist angle, which is characterized by complex interlayer hoppings at commensurate AA stackings (rather than the real hoppings in the BM model), a real interlayer hopping at commensurate AB/BA stackings, and a global energy shift. The complex phases of the AA stacking hoppings and the twist angle together define a single angle parameter phi(0). We compute the model parameters for the first six distinct commensurate TBG configurations, among which the 38.2 degrees configuration may be within experimentally observable energy scales. We identify the first magic angle for any phi(0) at a condition similar to that of the BM model. At this angle, the lowest two moire bands at charge neutrality become flat except near the Gamma(M) point and retain fragile topology but lose particle-hole symmetry. We further identify a hypermagic parameter regime centered at phi(0) = +/-pi/2 where many moire bands around charge neutrality (often 8 or more) become flat simultaneously. Many of these flat bands resemble those in the kagome lattice and p(x), p(y) 2-orbital honeycomb lattice tight-binding models.

【 授权许可】

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