Tunneling Spectroscopy of Superconducting States in Magic-Angle Twisted Bilayer Graphene

The discovery of correlated insulating states and unconventional superconductivity in the twisted bilayer graphene (TBG) systems has instigated numerous follow-up experiments and theories in the past year. However, the origin of the superconducting states, including the nature of the correlated insulating states, parent metallic states, pairing mechanism, size of the superconducting gap, etc. still remain greatly unknown. Recent scanning tunneling spectroscopy experiments have analyzed the local density of states in the insulating states, revealing the splitting of the van Hove singularities near half-filling and the breaking of rotational symmetry. Here, we develop highly tunable magic-angle TBG systems with various gate geometries that allow several different tunneling transport regimes within each device. The results of our tunneling spectroscopy experiments on the superconducting states are presented.