Moiré superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes^{1,2,3,4,5,6,7}, the confinement of excitons in artificial moiré lattices^{8,9,10,11,12,13} and the formation of exotic quantum phases^{14,15,16,17,18}. Such moiré-induced emergent phenomena are particularly strong for interlayer excitons, where the hole and the electron are localized in different layers of the heterostructure^19,20. To exploit the full potential of correlated moiré and exciton physics, a thorough understanding of the ultrafast interlayer exciton formation process and the real-space wavefunction confinement is indispensable. Here we show that femtosecond photoemission momentum microscopy provides quantitative access to these key properties of the moiré interlayer excitons. First, we elucidate that interlayer excitons are dominantly formed through femtosecond exciton–phonon scattering and subsequent charge transfer at the interlayer-hybridized Σ valleys. Second, we show that interlayer excitons exhibit a momentum fingerprint that is a direct hallmark of the superlattice moiré modification. Third, we reconstruct the wavefunction distribution of the electronic part of the exciton and compare the size with the real-space moiré superlattice. Our work provides direct access to interlayer exciton formation dynamics in space and time and reveals opportunities to study correlated moiré and exciton physics for the future realization of exotic quantum phases of matter.

原子级薄范德华异质结构中的莫尔超晶格对于延长电子和谷电子寿命的控制^{1,2,3,4,5,6,7}，人造莫尔晶格中激子的限制^{8,9,10,11 具有很大的希望， 12,13}和奇异量子相^{14,15,16,17,18}的形成。这种莫尔诱导的涌现现象对于层间激子特别强烈，其中空穴和电子位于异质结构的不同层中^19,20. 为了充分利用相关莫尔和激子物理的潜力，对超快层间激子形成过程和真实空间波函数限制的透彻了解是必不可少的。在这里，我们展示了飞秒光发射动量显微镜提供了对莫尔层间激子的这些关键特性的定量访问。首先，我们阐明了层间激子主要通过飞秒激子 - 声子散射和随后层间杂化 Σ 谷处的电荷转移形成。其次，我们表明层间激子表现出动量指纹，这是超晶格莫尔修饰的直接标志。第三，我们重建了激子电子部分的波函数分布，并将其尺寸与真实空间莫尔超晶格进行了比较。