莫尔石墨烯体系的新奇电学性质  

Novel electrical properties of moirégraphene systems

作　　者：张世豪 解博 彭然 刘晓迁 吕昕 刘健鹏 Zhang Shi-Hao;Xie Bo;Peng Ran;Liu Xiao-Qian;LüXin;Liu Jian-Peng(School of Physical Science and Technology,ShanghaiTech University,Shanghai 201210,China;Laboratory for Topological Physics,ShanghaiTech University,Shanghai 201210,China)

机构地区：[1]上海科技大学物质科学与技术学院,上海201210 [2]上海科技大学,拓扑物理实验室,上海201210

出　　处：《物理学报》2023年第6期246-267,共22页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12174257);国家重点研发计划(批准号:2020YFA0309601);上海科技大学启动经费资助的课题.

摘　　要：讨论了转角双层石墨烯、转角多层石墨烯以及石墨烯-绝缘态异质结等体系中的电子结构、拓扑性质、关联物态、非线性光学响应、声子特征以及电声耦合效应等新奇物态和物性.首先讨论了在转角石墨烯体系中普遍存在的拓扑非平庸的平带和轨道铁磁性.其中,魔角双层石墨烯中的拓扑平带可以从零赝朗道能级的图像去理解.该图像可以很简明地解释实验上观测到的量子反常霍尔效应、关联绝缘态等新奇现象.这些拓扑平带也可以带来接近量子化的拓扑压电响应,可以用来定量地测量莫尔石墨烯中平带的谷陈数.转角多层石墨烯和交错转角多层石墨烯体系也存在一些普适的手性分解规则,可快速判断这类转角石墨烯体系中低能电子结构特征.然后进一步讨论了魔角双层石墨烯和转角多层石墨烯中的关联绝缘态、密度波态、向列序态以及单粒子激发谱的级联转变等新奇物性,并提出非线性光学响应可以当作区分各类“无特征”关联绝缘态的实验探针.其次讨论了转角双层石墨烯体系的莫尔声子性质以及非平庸的电声耦合效应.最后,讨论了能带对齐的石墨烯和绝缘衬底形成的异质结体系中的新奇物理图景,并对二维材料莫尔异质结体系中的新奇物性做了总结和展望.In this review,we discuss the electronic structures,topological properties,correlated states,nonlinear optical responses,as well as phonon and electron-phonon coupling effects of moirégraphene superlattices.First,we illustrate that topologically non-trivial flat bands and moiréorbital magnetism are ubiquitous in various twisted graphene systems.In particular,the topological flat bands of magic-angle twisted bilayer graphene can be explained from a zeroth pseudo-Landau-level picture,which can naturally explain the experimentally observed quantum anomalous Hall effect and some of the other correlated states.These topologically nontrivial flat bands may lead to nearly quantized piezoelectric response,which can be used to directly probe the valley Chern numbers in these moirégraphene systems.A simple and general chiral decomposition rule is reviewed and discussed,which can be used to predict the low-energy band dispersions of generic twisted multilayer graphene system and alternating twisted multilayer graphene system.This review further discusses nontrivial interaction effects of magic-angle TBG such as the correlated insulator states,density wave states,cascade transitions,and nematic states,and proposes nonlinear optical measurement as an experimental probe to distinguish the different“featureless”correlated states.The phonon properties and electron-phonon coupling effects are also briefly reviewed.The novel physics emerging from band-aligned graphene-insulator heterostructres is also discussed in this review.In the end,we make a summary and an outlook about the novel physical properties of moirésuperlattices based on two-dimensional materials.

关 键 词：莫尔石墨烯异质结 拓扑物理 关联物态 莫尔声子 压电响应 非线性光学响应 

分 类 号：O613.71[理学—无机化学]