Atomically thin transition metal dichalcogenides (TMDs) are 2D semiconductors with tightly bound excitons and correspondingly strong light–matter interactions. Owing to the weak van der Waals bonding between layers, TMDs can be isolated and stacked together to form synthetic heterostructures with emergent electronic and excitonic properties. In this Review, we focus on the emergent exciton physics in moiré superlattices and in TMD heterobilayers coupled to optical cavities, where exciton behaviour can be dramatically modified by the environment. In moiré superlattices, a small twist angle or lattice mismatch between the layers introduces a periodic variation in the interlayer alignment that leads to exciton localization, modified optical selection rules and strong correlations. In cavity–heterostructure systems, light–matter interaction is enhanced and exciton states can couple to the cavity to form exciton-polaritons, whose properties depend on the specific TMD layers involved and their alignment. Here, we discuss recent theoretical and experimental progress towards realizing exotic exciton states in TMD heterobilayers and comment on future scientific and technological directions.

原子级薄的过渡金属二硫属化物 (TMD) 是二维半导体，具有紧密结合的激子和相应的强光-物质相互作用。由于层之间的范德华键弱，TMDs可以被隔离并堆叠在一起以形成具有新兴电子和激子特性的合成异质结构。在这篇综述中，我们关注莫尔超晶格和耦合到光学腔的 TMD 异质双层中的涌现激子物理，其中激子行为可以被环境显着改变。在莫尔超晶格中，层间的小扭转角或晶格失配会导致层间排列的周期性变化，从而导致激子定位、修改的光学选择规则和强相关性。在空腔异质结构系统中，光与物质的相互作用得到增强，激子态可以耦合到空腔以形成激子-极化子，其性质取决于所涉及的特定 TMD 层及其排列。在这里，我们讨论了在 TMD 异质双层中实现奇异激子态的最新理论和实验进展，并对未来的科学和技术方向发表评论。