Electric field-tunable superconductivity in alternating-twist magic-angle trilayer graphene

Engineering moiré superlattices by twisting layers in van der Waals (vdW) heterostructures has uncovered a wide array of quantum phenomena. We constructed a vdW heterostructure that consists of three graphene layers stacked with alternating twist angles ±θ. At the average twist angle θ ~ 1.56°, a th...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2021-03, Vol.371 (6534), p.1133-1138
Main Authors: Hao, Zeyu, Zimmerman, A M, Ledwith, Patrick, Khalaf, Eslam, Najafabadi, Danial Haie, Watanabe, Kenji, Taniguchi, Takashi, Vishwanath, Ashvin, Kim, Philip
Format: Article
Language:English
Subjects:
Electric fields
Flavor
Graphene
Superconductivity
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Summary:Engineering moiré superlattices by twisting layers in van der Waals (vdW) heterostructures has uncovered a wide array of quantum phenomena. We constructed a vdW heterostructure that consists of three graphene layers stacked with alternating twist angles ±θ. At the average twist angle θ ~ 1.56°, a theoretically predicted "magic angle" for the formation of flat electron bands, we observed displacement field-tunable superconductivity with a maximum critical temperature of 2.1 kelvin. By tuning the doping level and displacement field, we found that superconducting regimes occur in conjunction with flavor polarization of moiré bands and are bounded by a van Hove singularity (vHS) at high displacement fields. Our findings display inconsistencies with a weak coupling description, suggesting that the observed moiré superconductivity has an unconventional nature.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.abg0399