The eight Landau levels of bilayer graphene in a magnetic field near the charge neutrality point is a rich playground to explore the effect of competing many-body interactions. Studies have uncovered numerous level crossings that correspond to the change of the ground state ordering. Previous work from our group has established an empirical and quantitative energy diagram[1]. Here we report measurements on the Landau level energy gaps of bilayer graphene adjacent to 1-2 layer WSe₂ through van der Waals stacking. In comparison to pristine samples, a significant enhancement of the orbital splitting between the N=0 and N=1 levels was observed. The coincidence point of the ν=0 gap splits at field as low as 4T. Meanwhile, the magnitude of the large ν =2 gap was reduced to roughly half of its value in pristine bilayer. Using thermally activated transport and a pair of top and bottom gates, we performed a set of gap measurements at ν =1, 2, 3 as a function of the carrier density and the applied perpendicular electric field D. We analyze the dependences, compare to the results in pristine bilayer and discuss the impact of WSe₂.

[1] J. Li, Y. Tupikov, K. Watanabe, T. Taniguchi, and J. Zhu, Effective Landau Level Diagram of Bilayer Graphene, Phys. Rev. Lett. 120, 047701 (2018).