Every-other-layer dipolar excitons in a spin-valley locked superlattice
Every-other-layer dipolar excitons in a spin-valley locked superlattice
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DOI：
10.1038/s41565-023-01350-1
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发表时间：
2022-12
影响因子：
38.3
通讯作者：
Yinong Zhang;Chengxin Xiao;D. Ovchinnikov;Jiayi Zhu;Xi Wang;T. Taniguchi;Kenji Watanabe;Jiaqiang Yan;W. Yao;Xiaodong Xu
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作者：
Yinong Zhang;Chengxin Xiao;D. Ovchinnikov;Jiayi Zhu;Xi Wang;T. Taniguchi;Kenji Watanabe;Jiaqiang Yan;W. Yao;Xiaodong Xu
过渡金属双硫族化合物半导体单层膜具有破缺的反转对称性和强的自旋轨道耦合，导致独特的自旋谷锁定效应。在2 H堆叠的原始多层膜中，自旋谷锁定产生电子超晶格结构，其中交替层对应于势垒和量子威尔斯，这取决于自旋谷指数。在这里，我们表明，自旋谷锁定超晶格主机一种偶极激子与电子和空穴成分分离的每隔一层的配置：也就是说，无论是在两个偶数或两个奇数层。这种激子通过与层内激子杂交而变得光学明亮。这种效应也表现在反射光谱中存在多个反交叉图案，因为偶极激子通过电场通过层内共振进行调谐。反射光谱进一步揭示了每隔一层激子的激发态轨道，指向与层内激子相同数量级的相当大的结合能。随着层厚的增加，偶极激子可以形成一维玻色-哈伯德链，显示出层数依赖的精细光谱结构。
Monolayer semiconducting transition metal dichalcogenides possess broken inversion symmetry and strong spin-orbit coupling, leading to a unique spin-valley locking effect. In 2H stacked pristine multilayers, spin-valley locking yields an electronic superlattice structure, where alternating layers correspond to barriers and quantum wells depending on the spin-valley indices. Here we show that the spin-valley locked superlattice hosts a kind of dipolar exciton with the electron and hole constituents separated in an every-other-layer configuration: that is, either in two even or two odd layers. Such excitons become optically bright via hybridization with intralayer excitons. This effect is also manifested by the presence of multiple anti-crossing patterns in the reflectance spectra, as the dipolar exciton is tuned through the intralayer resonance by an electric field. The reflectance spectra further reveal an excited state orbital of the every-other-layer exciton, pointing to a sizable binding energy in the same order of magnitude as the intralayer exciton. As layer thickness increases, the dipolar exciton can form a one-dimensional Bose–Hubbard chain displaying layer number-dependent fine spectroscopy structures.