Symmetry breaking in twisted double bilayer graphene
Symmetry breaking in twisted double bilayer graphene
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DOI：
10.1038/s41567-020-1030-6
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发表时间：
2020-09-14
期刊：
影响因子：
19.6
通讯作者：
Yankowitz, Matthew
中科院分区：
文献类型：
--
作者：
He, Minhao;Li, Yuhao;Yankowitz, Matthew
输运测量表明，自发对称破缺在扭曲双双层石墨烯的相关绝缘态和金属态中起着至关重要的作用。在一些扭曲的范德华异质结构中出现的平坦带提供了一种环境，在这种环境中，电子之间的强相互作用导致了各种相关相（1-20）。特别是，扭曲双双层石墨烯的异质结构具有相关的绝缘状态，可以通过扭曲角度和外电场来调节（11-14）。在这里，我们报告了扭曲双双层石墨烯的电输运测量，我们研究了自发对称破缺在其相图中的基本作用。当温度降低时，每个相关绝缘体附近的金属态的电阻率会突然下降，并伴有相关的非线性电流-电压特性。尽管在性质上与超导相似，但霍尔系数符号的同时反转指向自发的对称性破缺，因为突然电阻率的起源下降，而焦耳加热似乎是非线性输运的基础。我们的研究结果表明，类似的机制可能与更广泛的半导体平带范德华异质结构有关。
Transport measurements show that spontaneous symmetry breaking plays a crucial role in the correlated insulating and metallic states in twisted double bilayer graphene.The flat bands that appear in some twisted van der Waals heterostructures provide a setting in which strong interactions between electrons lead to a variety of correlated phases(1-20). In particular, heterostructures of twisted double bilayer graphene host correlated insulating states that can be tuned by both the twist angle and an external electric field(11-14). Here, we report electrical transport measurements of twisted double bilayer graphene with which we examine the fundamental role of spontaneous symmetry breaking in its phase diagram. The metallic states near each of the correlated insulators exhibit abrupt drops in their resistivity as the temperature is lowered, along with associated nonlinear current-voltage characteristics. Despite qualitative similarities to superconductivity, the simultaneous reversals in the sign of the Hall coefficient point instead to spontaneous symmetry breaking as the origin of the abrupt resistivity drops, whereas Joule heating seems to underlie the nonlinear transport. Our results suggest that similar mechanisms are probably relevant across a broader class of semiconducting flat band van der Waals heterostructures.