Zero-field superconducting diode effect in twisted trilayer graphene

A zero-field superconducting diode effect is recently reported in twisted trilayer graphene, evidenced by the highly nonreciprocal I-V curve and directional dependence in the critical supercurrent [1]. This phenomenon points towards an electronic order in graphene moir'e systems that breaks both parity and time-reversal symmetry (PT-breaking). In this talk, I use a scheme of angle-resolved nonreciprocal transport response to identify the PT-breaking order in twisted trilayer graphene. By analyzing the evolution with varying magnetic field, moir'e band filling and current bias, I show that this PT-breaking order is distinct from orbital ferromagnetism. While the zero-field superconducting diode effect is observed over a wide range of twist angles, it is the most prominent when the twist angle is detuned from the magic-angle regime. To understand this unique twist angle dependence, I will discuss the subtle interplay between the moir'e flatband and Coulomb interaction, which gives rise to a new cascade order in the small twist angle regime.

[1] Jiang-Xiazi Lin, et al. "Zero-field superconducting diode effect in small-twist-angle trilayer graphene." Nature Physics 18, 10 (2022)