近日，美国伦斯勒理工学院的Su-Fei Shi及其研究小组与美国加州大学的Yong-Tao Cui等人合作并取得一项新进展。经过不懈努力，他们实现WS2/WSe2莫尔超晶格中的谷极化激子莫特绝缘子。相关研究成果已于2023年11月6日在国际知名学术期刊《自然—物理学》上发表。
该研究团队确定了层间激子的空间范围以及关联态的带层次。这种层间激子与WS2/WSe2莫尔超晶格中的关联电子之间存在强烈的排斥作用。进一步的实验观察发现，当层间激子占据一个莫尔单元时，会导致激子莫特绝缘态的出现。这种绝缘态下，谷极化提高了近一个数量级。这项研究结果表明，WS2/WSe2莫尔超晶格成为了一个极具潜力的平台，用于设计和探索费米子、玻色子以及两者混合的全新关联态。现有的证据已经表明，这些相互作用能够产生激子莫特绝缘体
据悉，过渡金属二硫系异质层形成的半导体莫尔超晶格中，电子-电子相互作用的增强引发了丰富而有趣的费米子关联态的涌现。值得注意的是，在II型排列的异质层莫尔超晶格中，当电子和空穴被分隔在不同的层中时，层间激子继承了这种增强的相互作用。这一重要特性揭示了一种可能性，即人们能够实现具备谷自由度的可调谐关联玻色子准粒子。
附：英文原文
Title: Valley-polarized exitonic Mott insulator in WS2/WSe2 moiré superlattice
Author: Lian, Zhen, Meng, Yuze, Ma, Lei, Maity, Indrajit, Yan, Li, Wu, Qiran, Huang, Xiong, Chen, Dongxue, Chen, Xiaotong, Chen, Xinyue, Blei, Mark, Taniguchi, Takashi, Watanabe, Kenji, Tongay, Sefaattin, Lischner, Johannes, Cui, Yong-Tao, Shi, Su-Fei
Issue&Volume: 2023-11-06
Abstract: The strongly enhanced electron–electron interactions in semiconducting moiré superlattices formed by transition metal dichalcogenide heterobilayers have led to a plethora of intriguing fermionic correlated states. Meanwhile, interlayer excitons in a type II aligned heterobilayer moiré superlattice, with electrons and holes separated in different layers, inherit this enhanced interaction and suggest that tunable correlated bosonic quasiparticles with a valley degree of freedom could be realized. Here we determine the spatial extent of interlayer excitons and the band hierarchy of correlated states that arises from the strong repulsion between interlayer excitons and correlated electrons in a WS2/WSe2 moiré superlattice. We also find evidence that an excitonic Mott insulator state emerges when one interlayer exciton occupies one moiré cell. Furthermore, the valley polarization of the excitonic Mott insulator state is enhanced by nearly one order of magnitude. Our study demonstrates that the WS2/WSe2 moiré superlattice is a promising platform for engineering and exploring new correlated states of fermion, bosons and a mixture of both. Interactions between excitons and correlated electrons can lead to the formation of interesting states. Now, evidence suggests that these interactions can give rise to a Mott insulator of excitons.
DOI: 10.1038/s41567-023-02266-2
Source: https://www.nature.com/articles/s41567-023-02266-2