Gate-tunable topological flat bands in twisted monolayer-bilayer graphene

Youngju Park, Bheema Lingam Chittari, Jeil Jung

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38 Scopus citations


We investigate the band structure of twisted monolayer-bilayer graphene (tMBG) trilayers, or twisted graphene on bilayer graphene, as a function of twist angles and perpendicular electric fields in search of optimal conditions for achieving isolated nearly flat bands. Narrow bandwidths comparable to or smaller than the effective Coulomb energies satisfying Ueff/W≳1 are expected for twist angles in the range of 0.3- -1.5- , more specifically in islands around θ∼0.5- ,0.85- ,1.3- for appropriate perpendicular electric field magnitudes and directions. The valley Chern numbers of the electron-hole asymmetric bands depend intrinsically on the details of the hopping terms in the bilayer graphene, and extrinsically on factors like electric fields or average staggered potentials in the graphene layer aligned with the contacting hexagonal boron nitride substrate. This tunability of the band isolation, bandwidth, and valley Chern numbers makes tMBG trilayers a more versatile system than twisted bilayer graphene for finding nearly flat bands prone to strong correlations.

Original languageEnglish
Article number035411
JournalPhysical Review B
Issue number3
StatePublished - 15 Jul 2020


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