Probing Superconductivity in Magic Angle Twisted Trilayer Graphene with Josephson Junctions Part 2

One of the outstanding questions in magic angle twisted graphene systems is the nature of the order parameter of the superconductivity that emerges in the flat bands. While there are hints that the superconductivity may be unconventional, further experiments are needed.  One method of answering this question is to use phase sensitive measurements of the superconductivity, which provide an important probe into the nature of the superconducting order parameter. In particular, phase sensitive measurements using fabricated Josephson junctions (JJs) have been crucial in demonstrating unconventional superconductivity in materials such as high temperature cuprate superconductors and UPt₃. Here we report our measurements of JJs between twisted trilayer graphene (TTG) and the conventional s-wave superconductor NbN. We observe a Fraunhofer pattern that arises from the JJ with a magnetic field period that is distinct from that of the intrinsic JJs in TTG. This period is larger than the JJ area as expected for 2D superconductors where flux penetration is controlled by the Pearl length. We will discuss how this Fraunhofer pattern is tuned by tuning the superconductivity in TTG. We will further discuss the controlled design of JJ geometry to probe the TTG superconducting order parameter.