Strange Metals from Melting Correlated Insulators in Twisted Bilayer Graphene
Strange Metals from Melting Correlated Insulators in Twisted Bilayer Graphene
复制标题
扭曲双层石墨烯中相关绝缘体熔化产生的奇怪金属
DOI：
10.1103/physrevlett.127.266601
复制
发表时间：
2021
影响因子：
8.6
通讯作者：
Kim, Eun-Ah
中科院分区：
文献类型：
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作者：
Cha, Peter;Patel, Aavishkar A.;Kim, Eun-Ah
即使对魔角扭曲双层石墨烯中相关绝缘态背后的机制的理解朝着各种自发对称性破缺收敛，绝缘转变温度以上的金属“正常态”仍然是神秘的，它具有过高的熵和线性温度电阻率。在这封信中，我们专注于在低能平带的整数填充描述相关绝缘态的序参数的波动对电荷输运的影响。出于观察的异质性的序参数景观在零磁场在某些样品中，我们推测存在令人沮丧的扩展范围的相互作用在一个有效的伊辛模型的序参数的三角形晶格。短距离铁磁相互作用和令人沮丧的扩展范围的反铁磁相互作用之间的竞争导致了一个新兴的长度尺度，形成条纹状的中尺度域以上的有序过渡。这些异质组态的无隙起伏被认为是负责的线性温度电阻率以及增强的低温熵。我们的见解链接实验观察到的线性温度电阻率和增强熵的挫折强度，或等效地，介观长度尺度表征序参数域的出现。
Even as the understanding of the mechanism behind correlated insulating states in magic-angle twisted bilayer graphene converges toward various kinds of spontaneous symmetry breaking, the metallic “normal state” above the insulating transition temperature remains mysterious, with its excessively high entropy and linear-in-temperature resistivity. In this Letter, we focus on the effects of fluctuations of the order parameters describing correlated insulating states at integer fillings of the low-energy flat bands on charge transport. Motivated by the observation of heterogeneity in the order-parameter landscape at zero magnetic field in certain samples, we conjecture the existence of frustrating extended-range interactions in an effective Ising model of the order parameters on a triangular lattice. The competition between short-distance ferromagnetic interactions and frustrating extended-range antiferromagnetic interactions leads to an emergent length scale that forms stripy mesoscale domains above the ordering transition. The gapless fluctuations of these heterogeneous configurations are found to be responsible for the linear-in-temperature resistivity as well as the enhanced low-temperature entropy. Our insights link experimentally observed linear-in-temperature resistivity and enhanced entropy to the strength of frustration or, equivalently, to the emergence of mesoscopic length scales characterizing order-parameter domains.