摘要
当两个晶格常数或晶格转角不同的二维材料叠加在一起时会出现周期性的莫尔条纹结构,这种莫尔超晶格形成了一个新的二维周期势,可以大大改变原有体系的物理性质.最近石墨烯与石墨烯、石墨烯与六方氮化硼形成的莫尔超晶格提供了一个非常有趣的体系,在该体系中石墨烯的电子能带结构发生了根本性的改变,在原本的能谷处产生了额外的超晶格小能带,由此产生了十分丰富的强关联效应和拓扑效应.本文介绍关于石墨烯莫尔超晶格体系拓扑性质的理论和实验研究进展,主要包括双层石墨烯的畴壁拓扑态、转角双层石墨烯的小能带拓扑态、ABC堆叠三层石墨烯以及转角双层堆叠双层石墨烯的拓扑性质等,最后介绍利用近场光学技术研究石墨烯莫尔超晶格体系的能带结构和新奇拓扑性质.
When 2D materials with different lattice constants or lattice rotation angles are stacked together,a periodic moirépattern will appear.Such moirésuperlattice introduces a new two dimensional periodic potential,which can greatly change the physical properties of the original systems.Recent experimental studies of moirésuperlattices formed by graphene on graphene and graphene on hexagonal boron nitride have revealed very rich strong correlation effects and topological effects due to novel states in superlattice minibands.It has been shown that flat bands in graphene-based moirésuperlattice systems can host both topological states and strongly correlated states,which can be controlled by an external electric field.In bilayer graphene,ABC stacked trilayer graphene and twisted bilayer-bilayer graphene,the number of valence and conduction bands near the Dirac point and even the band topology and bandwidth can be changed by varying the stacking angle between graphene layers or the applied bias voltage.Moreover,the competition between kinetic energy and coulomb interaction depends on the bandwidth and the external electric field,and at the so-called magic angle mott insulator states and superconductivity were observed.Twisted bilayer-bilayer graphene has also been predicted to show similar intriguing properties,including electrically tunable strongly correlated insulators,superconductivity and many rich topological states.In graphene-based moirésystems,the combination of topological states and strong correlations is expected to lead to a broad range of novel phenomena that are not achievable in other material systems.Therefore,graphene moirésystems is likely to bring substantial progress to the study of topological materials.In this paper,we review theoretical and experimental investigations of the topological properties of graphene moirésuperlattices,including topological domain wall states in bilayer graphene and topological effects in twisted bilayer graphene,ABC trilayer graphene and twisted double bilayer graphene.The origins of topological properties of these systems are discussed as well as topological phenomena observed in various experiments.Finally,recent near-field optical studies of the band structure and novel topological properties of graphene moirésuperlattices are discussed.
作者
吕新宇
李志强
LüXin-Yu;Li Zhi-Qiang(College of Physics,Sichuan University,Chengdu 610065,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第22期15-26,共12页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11874271)资助的课题~~
关键词
石墨烯
莫尔超晶格
拓扑
近场光学
graphene
moirésuperlattice
topology
near-field optics
作者简介
通信作者:李志强,E-mail:zhiqiangli@scu.edu.cn。
