Signatures of emergent interfacial superconductivity in 45-degree twisted van der Waals Cuprate Superconductors*

We developed a cryogenic assembly technique to fabricate Josephson Junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. Transport measurements probing the interface revealed a suppressed but finite critical current close to 45 degrees. Fraunhofer patterns revealed anomalous junction effective thickness, which can be explained by a theoretical analysis that incorporates the second harmonic in the Josephson Energy versus phase relation.  We study the change of Fraunhofer patterns as we vary applied in-plane magnetic field direction, probing the current distribution in the Josephson junction. Our theoretical analysis supports the dominant second harmonic in our Josephson Junctions, indicating time-reversal broken interfacial superconductivity.