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 moiré graphene, and suggests a way of directly probing the microscopic mechanisms of superconductivity in strongly correlated systems. 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.

中文翻译：

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解开魔角石墨烯中的绝缘和超导顺序

超导和相关绝缘状态在魔角扭曲双层石墨烯 1-11 中的共存引发了有关它们之间关系的有趣问题。独立控制控制这些阶段的微观机制可以帮助揭示它们各自的作用并阐明它们错综复杂的相互作用。在这里，我们通过改变石墨烯和金属屏蔽层 12、13 之间的分离距离来报告该系统中电子相互作用的直接调谐。我们观察到屏蔽层间距小于 15 纳米的典型万尼尔轨道尺寸且扭曲角略微偏离 1.10 ± 0.05 度的魔角的设备中相关绝缘体的淬火。在绝缘命令消失后，空出的相空间被超导圆顶接管，其临界温度可与具有强绝缘体的设备相媲美。此外，我们发现半填充的绝缘体可以在 0.4 特斯拉的小平面外磁场中重新出现，从而产生陈数为 2 的量子化霍尔态。我们的研究建议重新检查经常假设的莫尔石墨烯中绝缘相和超导相之间的“亲子”关系，并提出了一种直接探索强相关系统中超导微观机制的方法。通过改变扭曲双层石墨烯的介电环境来调整电子相互作用，揭示了绝缘状态的消失及其被超导相取代，表明两相之间存在竞争。