Double-dome Superconductivity in magic angle Twisted Trilayer Graphene

Moiré superconductivity has been observed in twisted bilayer and multilayer graphene systems. Among these, the twisted trilayer graphene (TTG) emerges as a particularly intriguing platform for studying moiré superconductivity. The flat-band physics in TTG mirrors that of twisted bilayer graphene while offering a tunable band structure, an extra knob to understand moiré superconductivity better. So far, unconventional superconductivity in TTG has been studied using transport and STM measurements. Here, we report displacement field tunable double-dome superconductivity in magic-angle twisted trilayer graphene. We found that superconductivity is suppressed near ν*=-2.6 in some displacement field regions. Through temperature, magnetic field, and current bias dependence, we reveal the distinct transport behavior of the right and left dome superconductivities and their corresponding normal states. The temperature dependence of the normal-state resistance and the I−V curves on either side of ν^∗ suggest a phase transition and the potentially distinct nature of superconductivity in the two domes. Hartree-Fock calculations incorporating mild strain yield an incommensurate Kekulé spiral state whose effective spin polarization peaks in the regime where superconductivity is suppressed in experiments. This allows us to draw conclusions about the normal state as well as the unconventional nature of the superconducting order parameter.