Transport study of interface effect between WSe₂ and magic angle twisted bilayer graphene

When two graphene crystals are rotated by the so-called magic angle, a moire flatband emerges where strong Coulomb correlation gives rise to a range of interesting phenomena such as the correlated insulators and superconductivity. The ground state properties in such a system is shown to be sensitively tunable by the encapsulating substrates. For example, aligning tBLG with the boron nitride substrate leads to intrinsic ferromagnetism, evidenced by the quantum anomalous Hall effect. In addition, close proximity with an insulating tungsten-diselendie (WSe₂) crystal is shown to stabilize the superconducting phase over a wide range of twist angles. Here we report the influence of the WSe₂ interface on correlated insulators in magic-angle tBLG. In such structures, transport measurements demonstrate unique tunability to the ground state properties, which is made possible by a dual-gated sample geometry. By exploring a multi-dimensional phase space as a function of carrier density, temperature, perpendicular electric field and parallel magnetic field, we show that the tBLG/WSe₂ heterostructure offers a versatile platform to study the interplay between electron correlation, magnetism and topology.