Kavli Affiliate: Jeffrey B. Neaton
| First 5 Authors: Tomojit Chowdhury, Aurélie Champagne, Fauzia Mujid, Patrick Knüppel, Zehra Naqvi
| Summary:
Bilayer crystals, built from monolayers of two-dimensional (2D) crystals with
different lattice orientations, generate interlayer potentials leading to
unique excitonic properties. However, the ability to tune the interlayer
potential is limited by the fixed covalent 2D lattice geometries. Synthetically
substituting one of the layers with an atomically thin molecular crystal could
substantially expand the design space for tuning the excitonic response,
enabled by explicit control of chemical and electronic structures of the
molecular building blocks. Here we report the large-scale synthesis of
four-atom-thick hybrid bilayer crystals (HBCs), comprising perylene-based
molecular and transition metal dichalcogenide (TMD) monolayer single crystals,
which show precise tuning of the HBC lattices at the molecular level. We
observe near-unity anisotropic photoluminescence, which is directly tuned by
specific molecular geometry and HBC composition. Our ab initio GW and
Bethe-Salpeter equation calculations show that the anisotropic emission
originates from delocalized and anisotropic hybrid excitons. These excitons
inherit characteristics from states associated with both the TMD and molecular
layers, resulting from a hybridized bilayer band structure of the HBC. By
introducing HBCs as a scalable solid-state platform, our work paves the way for
tunable interlayer energy landscapes achievable through direct synthesis,
opening up new frontiers in molecule-based quantum materials.
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