Correlated states in alternating twisted bilayer-monolayer-monolayer graphene heterostructure

Highly controlled electronic correlation in twisted graphene heterostructures has gained enormous research interests recently, encouraging exploration in a wide range of moire superlattices beyond the celebrated twisted bilayer graphene. Here we characterize correlated states in an alternating twisted Bernal bilayer-monolayer-monolayer graphene of similar to 1.74 degrees, and find that both van Hove singularities and multiple correlated states are asymmetrically tuned by displacement fields. In particular, when one electron per moire unit cell is occupied in the electron-side flat band, or the hole-side flat band (i.e., three holes per moire unit cell), the correlated peaks are found to counterintuitively grow with heating and maximize around 20 K - a signature of Pomeranchuk effect. Our multilayer heterostructure opens more opportunities to engineer complicated systems for investigating correlated phenomena.

Automated summary

Highly controlled electronic correlation in twisted graphene heterostructures has attracted significant attention recently. In this study, we investigate correlated states in an alternating twisted Bernal bilayer-monolayer-monolayer graphene and observe that van Hove singularities and multiple correlated states are asymmetrically tuned by displacement fields. Our findings also show that correlated peaks grow counterintuitively with heating and reach a maximum around 20 K, indicating the presence of the Pomeranchuk effect. This multilayer heterostructure provides new opportunities for studying correlated phenomena.