Polarization and charge-separation of moiré excitons in van der Waals heterostructures

Abstract

Twisted transition metal dichalcogenide (TMD) bilayers exhibit periodic moiré potentials, which can trap excitons at certain high-symmetry sites. At small twist angles, TMD lattices undergo an atomic reconstruction, altering the moiré potential landscape via the formation of large domains, potentially separating the charges in-plane and leading to the formation of intralayer charge-transfer (CT) excitons. Here, we employ a microscopic, material-specific theory to investigate the intralayer charge-separation in atomically reconstructed MoSe${}_2$-WSe${}_2$ heterostructures. We identify three distinct and twist-angle-dependent exciton regimes including localized Wannier-like excitons, polarized excitons, and intralayer CT excitons. We calculate the moiré site hopping for these excitons and predict a fundamentally different twist-angle-dependence compared to regular Wannier excitons - presenting an experimentally accessible key signature for the emergence of intralayer CT excitons. Furthermore, we show that the charge separation and its impact on the hopping can be efficiently tuned via dielectric engineering.

6 pages, 5 figures

References in corpus (21)

• Observation of Long-Lived Interlayer Excitons in Monolayer MoSe2-WSe2 Heterostructures
• Moiré excitons: from programmable quantum emitter arrays to spin-orbit coupled artificial lattices
• Imaging moiré flat bands in 3D reconstructed WSe2/WS2 superlattices
• Interlayer coupling in commensurate and incommensurate bilayer structures of transition metal dichalcogenides
• Tunable Phases of Moiré Excitons in van der Waals Heterostructures
• Excitons in mesoscopically reconstructed moiré heterostructures
• Rotational and Dilational Reconstruction in Transition Metal Dichalcogenide Moiré Bilayers
• Piezoelectric networks and ferroelectric moiré superlattice domains in twistronic WS${}_2$/MoS${}_2$ and WSe${}_2$/MoSe${}_2$ bilayers
• Moiré-Bose-Hubbard model for interlayer excitons in twisted transition metal dichalcogenide heterostructures
• Exciton landscape in van der Waals heterostructures
• Dielectric catastrophe at the Mott and Wigner transitions in a moiré superlattice
• Electrical tuning of moiré excitons in MoSe${}_2$ bilayers
• Interferences of electrostatic moiré potentials and bichromatic superlattices of electrons and excitons in transition metal dichalcogenides
• Band energy landscapes in twisted homobilayers of transition metal dichalcogenides
• Relaxation effects in twisted bilayer molybdenum disulfide: structure, stability, and electronic properties
• Spatially indirect intervalley excitons in bilayer WSe2
• Bosonic Delocalization of Dipolar Moiré Excitons
• Self-organised quantum dots in marginally twisted MoSe${}_2$/WSe${}_2$ and MoS${}_2$/WS${}_2$ bilayers
• Lattice reconstruction in MoSe${}_2$-WSe${}_2$ heterobilayers synthesized by chemical vapor deposition
• Impact of atomic reconstruction on optical spectra of twisted TMD homobilayers
• Optical Signatures of Moiré Trapped Biexcitons