Observation of moiré excitons in WSe2/WS2 heterostructure superlattices,Nature

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Observation of moiré excitons in WSe2/WS2 heterostructure superlattices
Nature ( IF 50.5 ) Pub Date : 2019-02-25 , DOI: 10.1038/s41586-019-0976-y
Chenhao Jin ₁ , Emma C Regan _{1,

2} , Aiming Yan _{1,

3} , M Iqbal Bakti Utama _{1,

4} , Danqing Wang _{1,

2} , Sihan Zhao ₁ , Ying Qin ₅ , Sijie Yang ₅ , Zhiren Zheng ₁ , Shenyang Shi _{1,

6} , Kenji Watanabe ₇ , Takashi Taniguchi ₇ , Sefaattin Tongay ₅ , Alex Zettl _{1,

3,

8} , Feng Wang _{1,

3,

8}

Affiliation

Moiré superlattices enable the generation of new quantum phenomena in two-dimensional heterostructures, in which the interactions between the atomically thin layers qualitatively change the electronic band structure of the superlattice. For example, mini-Dirac points, tunable Mott insulator states and the Hofstadter butterfly pattern can emerge in different types of graphene/boron nitride moiré superlattices, whereas correlated insulating states and superconductivity have been reported in twisted bilayer graphene moiré superlattices1–12. In addition to their pronounced effects on single-particle states, moiré superlattices have recently been predicted to host excited states such as moiré exciton bands13–15. Here we report the observation of moiré superlattice exciton states in tungsten diselenide/tungsten disulfide (WSe2/WS2) heterostructures in which the layers are closely aligned. These moiré exciton states manifest as multiple emergent peaks around the original WSe2 A exciton resonance in the absorption spectra, and they exhibit gate dependences that are distinct from that of the A exciton in WSe2 monolayers and in WSe2/WS2 heterostructures with large twist angles. These phenomena can be described by a theoretical model in which the periodic moiré potential is much stronger than the exciton kinetic energy and generates multiple flat exciton minibands. The moiré exciton bands provide an attractive platform from which to explore and control excited states of matter, such as topological excitons and a correlated exciton Hubbard model, in transition-metal dichalcogenides.Moiré superlattice exciton states are observed in WSe2/WS2 heterostructures with closely aligned layers.

中文翻译：

WSe2/WS2异质结构超晶格中莫尔激子的观察

莫尔超晶格能够在二维异质结构中产生新的量子现象，其中原子薄层之间的相互作用定性地改变了超晶格的电子能带结构。例如，在不同类型的石墨烯/氮化硼莫尔超晶格中可以出现微型狄拉克点、可调莫特绝缘体状态和霍夫施塔特蝴蝶图案，而在扭曲的双层石墨烯莫尔超晶格中已经报道了相关的绝缘状态和超导性 1-12。除了对单粒子状态的显着影响外，最近预测莫尔超晶格还具有激发态，例如莫尔激子带 13-15。在这里，我们报告了在层紧密排列的二硒化钨/二硫化钨 (WSe2/WS2) 异质结构中对莫尔超晶格激子态的观察。这些莫尔激子态表现为吸收光谱中原始 WSe2 A 激子共振周围的多个出现峰，并且它们表现出与 WSe2 单层和 WSe2/WS2 异质结构中的 A 激子不同的栅极依赖性。这些现象可以用一个理论模型来描述，其中周期性莫尔势比激子动能强得多，并产生多个平坦的激子微带。莫尔激子带提供了一个有吸引力的平台，可以从中探索和控制物质的激发态，例如拓扑激子和相关激子哈伯德模型，

更新日期：2019-02-25

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