Phase-sensitive signatures of time-reversal-symmetry-breaking superconductivity in magic-angle twisted trilayer graphene

We report phase-sensitive signatures consistent with time-reversal-symmetry-breaking superconductivity in magic-angle twisted trilayer graphene, using Josephson interferometry. Josephson junctions fabricated in both planar and corner geometries enable phase-sensitive comparison of Josephson coupling along distinct crystallographic directions. The resulting interference patterns exhibit strongly asymmetric critical current modulations and magnetic-field–sweep–direction hysteresis, signatures consistent with an unconventional superconducting state that breaks time-reversal symmetry. The asymmetry and hysteresis emerge only below a secondary transition temperature Tc* ∼ 0.8 K, distinctly lower than the superconducting onset at Tc ∼ 2 K, and strengthen upon further cooling. This temperature evolution is consistent with the emergence of an additional superconducting order-parameter component or a secondary time-reversal-symmetry-breaking instability within the superconducting phase. Our findings suggest that magic-angle twisted trilayer graphene is a promising platform to study time-reversal-symmetry-breaking superconductivity and possible chiral superconductivity, and demonstrate that Josephson interferometry provides a phase-sensitive probe of the phase structure of correlated two-dimensional moiré superconductors. The authors report phase-sensitive signatures consistent with time-reversal-symmetry-breaking chiral superconductivity in magic-angle twisted trilayer graphene, using Josephson interferometry. The time-reversal-symmetry-breaking signatures occur below 0.8 K, distinctly lower than the superconducting onset at Tc ∼ 2 K.