Exciton-exciton interactions in van der Waals heterobilayers

Abstract

Exciton-exciton interactions are key to understanding non-linear optical and transport phenomena in van der Waals heterobilayers, which emerged as versatile platforms to study correlated electronic states. We present a combined theory-experiment study of excitonic many-body effects based on first-principle band structures and Coulomb interaction matrix elements. Key to our approach is the explicit treatment of the fermionic substructure of excitons and dynamical screening effects for density-induced energy renormalization and dissipation. We demonstrate that dipolar blue shifts are almost perfectly compensated by many-body effects, mainly by screening-induced self-energy corrections. Moreover, we identify a crossover between attractive and repulsive behavior at elevated exciton densities. Theoretical findings are supported by experimental studies of spectrally-narrow interlayer excitons in atomically-reconstructed, hBN-encapsulated MoSe${}_2$/WSe${}_2$ heterobilayers. Both theory and experiment show energy renormalization on a scale of a few meV even for high injection densities in the vicinity of the Mott transition. Our results revise the established picture of dipolar repulsion dominating exciton-exciton interactions in van der Waals heterostructures and open up opportunities for their external design.

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• Two dimensional semiconductors: optical and electronic properties
• Electrically tunable and enhanced nonlinearity of moiré exciton-polaritons in transition metal dichalcogenide bilayers
• Exciton fractional Chern insulators in moiré heterostructures
• Striped excitonic (super)solid in anisotropic semiconductors with screened exciton interactions
• Electrically tunable MoSe${}_2$/WSe${}_2$ heterostructure-based quantum dot
• Intersubband electric dipole spin resonance in transition metal dichalcogenide heterobilayers
• Variational and field-theoretical approach to exciton-exciton interactions and biexcitons in semiconductors
• Ferroelectric Control of Interlayer Excitons in 3R-MoS${}_2$ / MoSe${}_2$ Heterostructures
• Tracking the photoinduced dynamics of a dark excitonic state in single-layer WS${}_2$ via resonant Autler-Townes splitting
• Effective long-range attraction of moiré excitons under the influence of atomic reconstructions and anisotropic screening
• Quantum siphoning of finely spaced interlayer excitons in reconstructed MoSe2/WSe2 heterostructures