Experimental detection of vortices in magic-angle graphene.

Superconducting magic-angle twisted-layer graphene (MATLG) is a promising candidate for superconducting electronics due to its electrical tunability. While the microscopic origins of superconductivity in MATLG have been intensively studied, many aspects of its phenomenology remain unexplored due to the challenges associated with studying two-dimensional (2D) materials. Here, we report the first direct experimental evidence of superconducting vortices in MATLG, a hallmark of type-II superconductors. Field-dependent critical current measurements in a gate-tuned Josephson junction reveal Fraunhofer-like patterns characteristic of ultrathin films with weak transverse screening. These patterns exhibit sudden shifts attributed to spontaneous vortex penetration into the leads. With the leads at the edge of the superconducting dome, we observe bistable V-I fluctuations linked to rapid vortex dynamics. Time-dependent measurements provide the vortex energy scale, the London penetration depth, and superfluid stiffness, consistent with recent kinetic inductance studies. These findings establish gate-defined Josephson junctions as versatile sensors of vortex dynamics in 2D superconductors.