Spectroscopy of a Tunable Moiré System with a Correlated and Topological Flat Band*

Moiré superlattices created by twisted stacking of 2D materials can host highly tunable electronic structure. In twisted bilayer graphene, the twist angle has been proven a powerful knob to tune the electron bandwidth. When the twisted angle is close to the magic angle (~1.1degree), the non-trivial correlated insulating phase and the superconductivity emerge. Besides twisted angle another tuning knob – electric field can also be effective. In twisted double bilayer (TDBG) which is made by twisting two Bernal bilayer graphene, the electric field can gap the Bernal bilayer graphene and change the band structure. In previous studies, multiple correlated insulators have been found in the multi-dimension phase diagram. Here we report the STM study of TDBG[1]. With the gate-tuned scanning tunneling spectroscopy, we reveal the single particle band structure under different twist angle which is hard to measure otherwise. Also, we will show, under certain conditions, the evidence of correlated insulating phase and giant orbital g-factor that arises from the valley Chern bands.

[1] arXiv:2008.07552