Probing correlations in the exciton landscape of a moiré heterostructure

Abstract

Excitons are two-particle correlated bound states that are formed due to Coulomb interaction between single-particle holes and electrons. In the solid-state, cooperative interactions with surrounding quasiparticles can strongly tailor the exciton properties and potentially even create new correlated states of matter. It is thus highly desirable to access such cooperative and correlated exciton behavior on a fundamental level. Here, we find that the ultrafast transfer of an exciton's hole across a type-II band-aligned moiré heterostructure leads to a surprising sub-200-fs upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this unusual upshift is a clear fingerprint of the correlated interactions of the electron and hole parts of the exciton quasiparticle. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access exciton correlations and cooperative behavior in two-dimensional quantum materials. Our work highlights this new capability and motivates the future study of optically inaccessible correlated excitonic and electronic states in moiré heterostructures.

32 pages, 4 main figures, 5 supplemental figures

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Cited by in corpus (8)

• Observation of Floquet states in graphene
• Ultrafast nano-imaging of dark excitons
• Twisted MoSe2 Homobilayer Behaving as a Heterobilayer
• Probing excitons with time-resolved momentum microscopy
• Hybrid Frenkel-Wannier excitons facilitate ultrafast energy transfer at a 2D-organic interface
• Review: Advanced characterization of the spatial variation of moiré heterostructures and moiré excitons
• Interface engineering of van der Waals heterostructures towards energy-efficient quantum devices operating at high temperatures
• Optical excitations in nanographenes from the Bethe-Salpeter equation and time-dependent density functional theory: absorption spectra and spatial descriptors