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Doped Twisted Bilayer Graphene near Magic Angles: Proximity to Wigner Crystallization, Not Mott Insulation
Nano Letters ( IF 9.6 ) Pub Date : 2018-09-05 00:00:00 , DOI: 10.1021/acs.nanolett.8b02033 Bikash Padhi 1 , Chandan Setty 1 , Philip W. Phillips 1
Nano Letters ( IF 9.6 ) Pub Date : 2018-09-05 00:00:00 , DOI: 10.1021/acs.nanolett.8b02033 Bikash Padhi 1 , Chandan Setty 1 , Philip W. Phillips 1
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We devise a model to explain why twisted bilayer graphene exhibits insulating behavior when ν = 2 or 3 charges occupy a unit moiré cell, a feature attributed to Mottness per previous work but not for ν = 1, clearly inconsistent with Mott insulation. We compute rs = EU/EK, where EU and EK are the potential and kinetic energies, respectively, and show that (i) the Mott criterion lies at a density larger than experimental values by a factor of 104 and (ii) a transition to a series of Wigner crystalline states exists as a function of ν. We find that, for ν = 1, rs fails to cross the threshold (rs = 37) for the triangular lattice, and metallic transport ensues. However, for ν = 2 and ν = 3, the thresholds rs = 22 and rs = 17, respectively, are satisfied for a transition to Wigner crystals (WCs) with a honeycomb (ν = 2) and a kagome (ν = 3) structure. We posit that such crystalline states form the correct starting point for analyzing superconductivity.
中文翻译：
接近魔角的掺杂扭曲双分子层石墨烯：接近威格纳晶化，而不是莫特绝缘
我们设计了一个模型来解释为什么当ν= 2或3个电荷占据一个莫尔单元时，扭曲的双层石墨烯会表现出绝缘行为，这是以前的工作归因于Mottness而不是ν= 1时明显与Mott绝缘不一致的特征。我们计算r s = E U / E K，其中E U和E K分别是势能和动能，并且表明（i）Mott准则的密度比实验值大10 4倍，并且（ii）向一系列维格纳晶态的转变是ν的函数。我们发现，对于ν= 1，r s未能超过三角形晶格的阈值（r s = 37），随后发生金属迁移。但是，对于ν= 2和ν= 3，分别满足阈值r s = 22和r s = 17，以过渡到具有蜂窝状（ν= 2）和kagome（ν= 3）结构。我们认为，这种晶态构成了分析超导性的正确起点。
更新日期：2018-09-05
中文翻译：
接近魔角的掺杂扭曲双分子层石墨烯：接近威格纳晶化，而不是莫特绝缘
我们设计了一个模型来解释为什么当ν= 2或3个电荷占据一个莫尔单元时，扭曲的双层石墨烯会表现出绝缘行为，这是以前的工作归因于Mottness而不是ν= 1时明显与Mott绝缘不一致的特征。我们计算r s = E U / E K，其中E U和E K分别是势能和动能，并且表明（i）Mott准则的密度比实验值大10 4倍，并且（ii）向一系列维格纳晶态的转变是ν的函数。我们发现，对于ν= 1，r s未能超过三角形晶格的阈值（r s = 37），随后发生金属迁移。但是，对于ν= 2和ν= 3，分别满足阈值r s = 22和r s = 17，以过渡到具有蜂窝状（ν= 2）和kagome（ν= 3）结构。我们认为，这种晶态构成了分析超导性的正确起点。
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