Interlayer coupling of moiré superconductivity

The discovery of emergent phenomena in moiré superlattices has opened a new door to study strongly correlated physics in two-dimensional (2D) systems. In particular, magic-angle twisted graphene superlattices have shown robust superconducting states with orders of magnitude higher transition temperatures than those in other graphene-based superconductors, as well as having displayed ultrastrong coupling and large violations of the Pauli limit, and exhibited signatures of unconventional pairing in tunneling spectroscopy. However, the exact nature and origin of the superconductivity are yet to be known. Here, we create a novel structure that vertically couples two magic-angle graphene superlattices in a localized region, where the carrier density in each magic-angle graphene layer, as well as the tunneling between the two layers, can be controlled independently. Interactions between the two layers in both the tunneling regime and the Josephson regime reveal the intricate nature of superconductivity and correlated states. Our results pave a new way to study 2D quantum materials and provide a potential platform for realizing a clean vertical tunnel junction in superconducting circuits for qubits.