We construct a van der Waals heterostructure consisting of three graphene layers stacked with alternating twisting angles ±θ. At the average twist angle θ∼1.56∘, a theoretically predicted magic angle for the formation of flat electron bands, narrow conduction and valence moir\'e bands appear together with a linearly dispersing Dirac band. Upon doping the half-filled moir\'e valence band with holes, or the half-filled moir\'e conduction band with electrons, displacement field tunable superconductivity emerges, reaching a maximum critical temperature of 2.1 K at optimal doping and displacement field. By tuning the doping level and displacement fields, we find that superconducting regimes occur in conjunction with flavour polarization of moir\'e bands bounded by a van Hove singularity (vHS) at high displacement fields. This experimental observation is found to be inconsistent with a weak coupling description, suggesting that the observed moir\'e superconductivity has an unconventional nature.
@article{arxiv.2012.02773,
title = {Electric field tunable unconventional superconductivity in alternating twist magic-angle trilayer graphene},
author = {Zeyu Hao and A. M. Zimmerman and Patrick Ledwith and Eslam Khalaf and Danial Haie Najafabadi and Kenji Watanabe and Takashi Taniguchi and Ashvin Vishwanath and Philip Kim},
journal= {arXiv preprint arXiv:2012.02773},
year = {2021}
}