Gate-Tunable Josephson Diodes in Magic-Angle Twisted Bilayer Graphene.

We report low-temperature measurements of two adjacent, gate-defined Josephson junctions (JJs) in magic-angle twisted bilayer graphene (MATBG) at a moiré filling factor near ν = -2. We show that both junctions exhibit a prominent, gate-tunable Josephson diode effect, which we explain by a combination of large kinetic inductance and nonuniform supercurrent distribution. Despite their proximity, the JJs display differences in their interference patterns and different diode behaviors, underscoring that microscopic inhomogeneities such as twist angle variations shape the nonuniform supercurrent and drive the diode behavior. As a result, the nonreciprocal supercurrent can be tuned by the gate voltage, enabling tuning of the diode efficiency and even reversing the polarity at fixed magnetic fields. Our findings offer potential routes for tailoring Josephson diode performance in superconducting quantum circuits.