Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening
Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening
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DOI：
10.1126/science.abb8754
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发表时间：
2021-03-19
期刊：
影响因子：
56.9
通讯作者：
Li, J. I. A.
中科院分区：
文献类型：
--
作者：
Liu, Xiaoxue;Wang, Zhi;Li, J. I. A.
控制相互作用的强度对于研究相关费米子系统中出现的量子现象至关重要。我们介绍了一种设备的几何形状，其中魔角扭曲的双层石墨烯被放置在靠近伯纳尔双层石墨烯，由3纳米厚的屏障分开。通过使用来自Bernal双层的电荷屏蔽，可以连续地调谐扭转双层内的电子-电子库仑相互作用的强度。输运测量表明，调谐库仑屏蔽对绝缘态和超导态有相反的影响：由于库仑相互作用被屏蔽削弱，绝缘态变得不那么鲁棒，而在最佳掺杂下的超导稳定性增强。这些结果为理解魔角扭曲双层石墨烯的超导机制提供了重要的理论模型约束。
Controlling the strength of interactions is essential for studying quantum phenomena emerging in systems of correlated fermions. We introduce a device geometry whereby magic-angle twisted bilayer graphene is placed in close proximity to a Bernal bilayer graphene, separated by a 3-nanometer-thick barrier. By using charge screening from the Bernal bilayer, the strength of electron-electron Coulomb interaction within the twisted bilayer can be continuously tuned. Transport measurements show that tuning Coulomb screening has opposite effects on the insulating and superconducting states: As Coulomb interaction is weakened by screening, the insulating states become less robust, whereas the stability of superconductivity at the optimal doping is enhanced. The results provide important constraints on theoretical models for understanding the mechanism of superconductivity in magic-angle twisted bilayer graphene.