Untying the insulating and superconducting orders in magic-angle graphene
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
The coexistence of superconducting and correlated insulating states in magic-angle twisted bilayer graphene1-11 prompts fascinating questions about their relationship. Independent control of the microscopic mechanisms that govern these phases could help uncover their individual roles and shed light on their intricate interplay. Here we report on direct tuning of electronic interactions in this system by changing the separation distance between the graphene and a metallic screening layer12,13. We observe quenching of correlated insulators in devices with screening layer separations that are smaller than the typical Wannier orbital size of 15 nanometres and with twist angles that deviate slightly from the magic angle of 1.10 ± 0.05 degrees. Upon extinction of the insulating orders, the vacated phase space is taken over by superconducting domes that feature critical temperatures comparable to those in devices with strong insulators. In addition, we find that insulators at half-filling can reappear in small out-of-plane magnetic fields of 0.4 tesla, giving rise to quantized Hall states with a Chern number of 2. Our study suggests re-examination of the often-assumed 'parent-and-child' relation between the insulating and superconducting phases in moiré graphene, and suggests a way of directly probing the microscopic mechanisms of superconductivity in strongly correlated systems.
Date Issued
2020-07-16
Date Acceptance
2020-04-17
Citation
Nature, 2020, 583, pp.375-378
ISSN
0028-0836
Publisher
Nature Research
Start Page
375
End Page
378
Journal / Book Title
Nature
Volume
583
Copyright Statement
© 2020 Springer Nature Limited.
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/32632215
PII: 10.1038/s41586-020-2459-6
Grant Number
EP/S025324/1
Subjects
General Science & Technology
Publication Status
Published
Coverage Spatial
England
Date Publish Online
2020-07-06