Landau Levels of Bilayer Graphene in a WSe$_2$/Bilayer Graphene van der Waals Heterostructure

Heterostructures formed between two different van der Waals materials enable interactions and functionalities absent in each component. In this work we show that vicinity to an atomically thin WSe$_2$ sheet dramatically impacts the energies of the symmetry-broken low Landau levels of bilayer graphene, possibly due to screening. We present a systematic study of the magnetic field and electrical displacement field dependences of the Landau level gaps at filling factor $ν$ = 1, 2, 3, and compare to BN encapsulated pristine bilayer graphene. The exchange-dominated energy splitting between the N = 0 and 1 orbital wave functions is significantly enhanced, which leads to a modified phase diagram at filling factor $ν$ = 0 and larger energy gaps at $ν$ = 1 and 3 in WSe$_2$/bilayer graphene heterostructures. The exchange-enhanced spin gap at $ν$ = 2, on the other hand, is reduced by approximately two-fold. Our results demonstrate a possible way to engineer quantum Hall phenomena via van der Waals heterostructures.