Quantum mechanics

Materials science

Trion

Superlattice

Scattering

Atomic physics

Position and momentum space

Laser

Physics

Brillouin zone

Exciton

Optics

Superconductivity

Condensed matter physics

Exciton-polaritons

Biexciton

Heterojunction

Wave function

Quasiparticle

Femtosecond

Nature

Moiré superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes1–7, the confinement of excitons in artificial moiré lattices8–13 and the formation of exotic quantum phases14–18. Such moiré-induced emergent phenomena are particularly strong for interlayer excitons, where the hole and the electron are localized in different layers of the heterostructure19,20. 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. Multidimensional time- and angle-resolved photoelectron spectroscopy is used to determine the interlayer exciton formation process, reveal a direct hallmark of the superlattice moiré modification, and reconstruct the real-space wavefunction distribution.

Formation of moiré interlayer excitons in space and time