We provide theoretical evidence of the emergent topology in a twisted bilayer system, despite the corresponding monolayer hosting topologically trivial properties. To this end, we investigate an interesting interplay of destructive interference due to lattice geometry and band folding due to enlargement of the unit cell in generating and subsequently modifying the band topology in a twisted bilayer $\alpha -T_3$ system. The large degeneracy of the emergent flat band in the dice limit of the $\alpha -T_3$ lattice is removed by aligning with h-BN layers, resulting in the formation of sub-bands with varied topological characteristics. Remarkably, while the sub-band near charge neutrality exhibits a trivial behavior, a topologically nondegenerate singular sub-band emerges away from it. The topological band remains isolated from the rest of the bands for a substantial area in the $\alpha -\theta$ plane (where $\alpha$ and $\theta$ correspond to the hopping ratio and twist angle, respectively) while exhibiting multiple phase transitions as a function of the aforementioned parameters via hybridization with its nearest bands. Finally, we study the evolution of the hybrid Wannier charge center and the Chern number to characterize the different emergent topological phases and corroborate our findings.

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• Chern number
• Flat bands
• Topological materials
• Topological phase transition
• Topological phases of matter
• Moire materials
• Twisted bilayers
• Lattice models in condensed matter