期刊
NATURE
卷 583, 期 7816, 页码 375-+出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/s41586-020-2459-6
关键词
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资金
- Ministry of Economy and Competitiveness of Spain through the Severo Ochoa programme for Centres of Excellence in RD [SE5-0522]
- Fundacio' Privada Cellex
- Fundacio' Privada Mir-Puig
- Generalitat de Catalunya through the CERCA program
- H2020 Programme [820378]
- Project 2D.SIPC
- La Caixa Foundation
- Science and Technology Center for Integrated Quantum Materials, NSF [DMR-1231319]
- Army Research Office [W911NF-18-1-0116]
- ERC consolidator grant TOPONANOP [726001]
- Elemental Strategy Initiative by MEXT, Japan
- CREST, JST [JPMJCR15F3]
- European Union's Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant [754510]
- European Research Council (ERC) [726001] Funding Source: European Research Council (ERC)
- EPSRC [EP/S025324/1] Funding Source: UKRI
Tuning the electronic interactions by changing the dielectric environment of twisted bilayer graphene reveals the disappearance of the insulating states and their replacement by superconducting phases, suggesting a competition between the two phases. The coexistence of superconducting and correlated insulating states in magic-angle twisted bilayer graphene(1-11)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 layer(12,13). 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 moire graphene, and suggests a way of directly probing the microscopic mechanisms of superconductivity in strongly correlated systems.
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