Tunable multi-bands in twisted double bilayer graphene

The bandstructure of a material, playing an important role in its electron transport property, is usually governed by the lattice configuration. Materials with a field-effect tunable band, such as bilayer [1] and rhombohedral trilayer graphene [2, 3], are more flexible for electronic applications. Here, on dual-gated twisted double bilayer graphene (TDBG) samples with small twist angle around 1(circle), we observe vertical electric-field-tunable bandstructures at multiple moire fillings with bandgap values continuously varying from zero to tens of mili-electron volts. Moreover, within the first moire filling on both electron and hole sides, the carrier transport deviates from Fermi liquid behavior, with measured resistivity exhibiting linear temperature dependence between 1.5 K and 50 K. Furthermore, under a vertical magnetic field, the coupling between the two bilayer graphene layers can also be turned on and off by a displacement field. Our results suggest TDBG with small twist angle is a platform for studying the evolution of multiple electric field tunable moire bands and the resulting emergent correlated electronic phases.

Automated summary

The bandstructure of a material, governed by its lattice configuration, plays a crucial role in electron transport. Materials with field-effect tunable band, such as bilayer and rhombohedral trilayer graphene, offer more flexibility for electronic applications. In this study, we observed vertically electric-field tunable bandstructures on dual-gated twisted double bilayer graphene samples, with bandgap values continuously varying from zero to tens of milli-electron volts. We also found that the carrier transport deviates from Fermi liquid behavior within the first moire filling under both electron and hole sides. Additionally, the coupling between the two bilayer graphene layers can be turned on and off by a displacement field under a vertical magnetic field. Our results suggest that twisted double bilayer graphene with small twist angle serves as a platform for studying the evolution of multiple electric field tunable moire bands and emergent correlated electronic phases.