Zero-field superconducting diode effect in small-twist-angle trilayer graphene

The critical current of a superconductor can be different for opposite directions flow when both time-reversal and inversion symmetry are broken. Such non-reciprocal behaviour creates superconducting diode has recently been experimentally demonstrated by breaking these symmetries with an applied magnetic field or the construction tunnel junction. Here we report intrinsic effect that is present at zero external in mirror-symmetric twisted trilayer graphene. behaviour, sign reversed through training out-of-plane field, provides direct evidence microscopic coexistence between superconductivity breaking. In addition to magnetic-field trainability, show zero-field controlled varying carrier density twist angle. A natural interpretation origin imbalance valley occupation underlying Fermi surface, which probably leads finite-momentum Cooper pairing nematicity phase. observed This suggests intrinsically broken electrons non-zero centre-of-mass momentum.