莫尔晶格中的激子绝缘体  

SPECIAL TOPIC-Two dimensional twisted moirésuperlattice Exciton insulator in a moirélattice

作　　者：古杰 马立国 Gu Jie;Ma Li-Guo(State Key Laboratory of Surface Physics,Department of Physics,Fudan University,Shanghai 200433,China;School of Applied and Engineering Physics,Cornell University,Ithaca 14850,USA)

机构地区：[1]复旦大学物理系,应用表面物理国家重点实验室,上海200433 [2]康奈尔大学应用物理系,伊萨卡14850

出　　处：《物理学报》2023年第6期225-236,共12页Acta Physica Sinica

摘　　要：当载流子动能被抑制后,双层量子阱中的电子-空穴可以通过层间库仑相互作用形成激子绝缘体,而抑制动能的主要手段为施加外部磁场产生朗道能级.在二维莫尔晶格中通过能带折叠可以显著抑制载流子动能进而形成莫尔平带.本文主要介绍通过莫尔平带实现无外加磁场的激子绝缘体,着重介绍几个不同的实验思路,并展示如何利用差分反射谱、层间激子光致发光谱、2s激子探测谱、量子电容以及微波阻抗谱探测激子绝缘体信号.总的来说,莫尔晶格中形成的激子绝缘体为在固体环境中研究Bose-Hubbard模型提供了很好的平台,其研究内容可包括激子莫特绝缘体、激子超流以及它们之间的连续转变等.Interlayer electron and hole can be paired up through coulomb interaction to form an exciton insulator when their kinetic energy is substantially smaller than the interaction energy.The traditional platform to realize such an interlayer interaction is the double quantum well with dielectric material between electron and hole,for which an external magnetic field is required to generate Landau level flat bands that can reduce the kinetic energy of charged carriers.When both quantum wells are at the half filling of the lowest landau level,the electron-electron repulsive interaction,by the particle-hole transformation in one well,will be equivalent to electron-hole attractive interaction,from which interlayer exciton and its condensation can emerge.In a two-dimensional twisted homostructure or an angle aligned heterostructure,there exists a moirésuperlattice,in which bands are folded into the mini-Brillouin zone by the large moiréperiod.Gap opening at the boundary of mini-Brillouin zone can form the well-known moiréflat band.This review will discuss how to use the moiréflat bands to generate exciton insulator in the absence of external magnetic field in transitional metal dichalcogenide(TMD)moiréheterostructure.Unlike the double quantum well where symmetric well geometry is used,the moirérelated sample can have multiple different geometries,including monolayer TMD-hexagonal boron nitride-moiréstructure,moiré-moiréstructure,and monolayer TMD-bilayer TMD structure.The carriers in those structures can be well tuned to locate equally in different layers,and particle-hole transformation in the moiréfirst Hubbard band can transform the interlayer repulsive coulomb interaction into attractive interaction,which is the same as that in quantum well under magnetic field.We will show that by using differential contrast reflection spectrum,interlayer photoluminescence,2s exciton sensing,quantum capacitance and microwave impedance microscopy,the signature of exciton fluid can be identified.The excitonic coherence feature

关 键 词：激子绝缘体 莫尔晶格 平带 二维半导体 

分 类 号：O469[理学—凝聚态物理]