Large Tunable Kinetic Inductance in a Twisted Graphene Superconductor

Twisted graphene based moiré heterostructures host a flat band at the magic angles where the kinetic energy of the charge carriers is quenched and interaction effects dominate. This results in emergent phases such as superconductors and correlated insulators that are electrostatically tunable. We investigate superconductivity in twisted trilayer graphene by integrating it as the weak link in a superconducting quantum interference device. The measured current phase relation yields a large and tunable kinetic inductance, up to 150 nH per square, of the electron and hole-type intrinsic superconductors. We further show that the specific kinetic inductance and the critical current density are universally related via the superconducting coherence length, and extract an upper bound of ∼200  nm for the coherence length. We discuss the implications of a large coherence length in twisted graphene superconductors.