Layers of two-dimensional materials stacked with a small twist-angle give rise to beating periodic patterns on a scale much larger than the original lattice, referred to as a "moire superlattice". As the twist angle approaches ~1.08 degree, isolated flat-bands emerge near zero energy. Correlated superconducting and insulating states were reported near the half-filling of such flat-bands. In this talk, we will discuss a higher-order moiré superlattice of moiré superlattices in a twisted-trilayer graphene architecture. We report superconducting and correlated insulating states near the half filling of the moire of moire superlattice, at an extremely low carrier density on the order of ~1010 cm-2. We also show that the temperature dependence of v=-4 and v=4 states are semi-metallic, distinct from the insulating behavior in twisted bilayer systems, demonstrating that moiré superconductivity can emerge from continuous and non-isolated flat-bands. Finally, we report robust superconductivity with critical temperature of 3.4 K despite the extremely low carrier density, implying that the origin of the strong correlation may primarily arise from factors other than large flat-band degeneracy.
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