Strong electronic correlations and Unconventional superconductivity in Magic-angle Twisted Trilayer Graphene

Flat electronic bands of magic-angle twisted trilayer graphene (MATTG) host correlated insulating states and unconventional superconductivity upon doping a few electrons per moire site. However, the exact nature of these states remains elusive to electric transport measurements. Measuring the dI/dV spectrum with scanning tunneling microscopy on MATTG reveals a cascade of electronic transitions and doping-dependent band deformations similar to magic angle bilayers. Upon doping away from the insulating state at half-filling, the gapped spectrum observed at two to three holes per moire site corresponds to superconductivity as verified through point contact spectroscopy showing signatures of Andreev reflection. Moreover, the superconducting gap shows several signatures suggesting the unconventional nature of superconductivity in MATTG, including unusual gap suppression with the temperature and a transition from a U-shaped to a V-shaped profile with doping. Our high-resolution local spectroscopic measurements can help establish the nature of correlated insulating and superconducting states in twisted graphene systems.