Realization of a Josephson Junction in magic-angle twisted 4-layer graphene

Alternating-twist magic-angle multilayer graphene structures have been experimentally confirmed as a family of moiré superconductors [1,2]. Like its bilayer counterpart, this class of materials exhibits electrostatically tunable superconductivity. Here, we electrostatically define a Josephson junction in magic-angle twisted 4-layer graphene by tuning the global density to a superconducting phase and, locally, a junction region to a resistive phase [1,3]. We measure the critical current of the junction as a function of the applied magnetic field and observe Fraunhofer pattern-like oscillations, whose periodicity matches the theoretical predictions for thin edge-type Josephson junctions [4]. We study the magnetic interference patterns not only as a function of electron density but also of displacement field. Unlike for the bilayer case, the latter affects superconductivity of 4-layer graphene. Our sample displays large critical currents (> 200 nA) and large stability in gate voltage range.

[1] Park, J.M. et al. Robust superconductivity in magic-angle multilayer graphene family. Nature Materials 21.8, 877-883 (2022)

[2] Zhang, Y. et al. Promotion of superconductivity in magic-angle graphene multilayers. Science 377.6614, 1538-1543 (2022)

[3] de Vries, F.K. et al. Gate-defined Josephson junctions in magic-angle twisted bilayer graphene. Nature Nanotechnology 16.7, 760-763 (2021)

[4] Moshe, M. et al.. Edge-type Josephson junctions in narrow thin-film strips. Physical Review B 78.2 (2008)