Visualizing band structure hybridization and superlattice effects in twisted MoS${}_2$/WS${}_2$ heterobilayers

Abstract

A mismatch of atomic registries between single-layer transition metal dichalcogenides (TMDs) in a two dimensional van der Waals heterostructure produces a moiré superlattice with a periodic potential, which can be fine-tuned by introducing a twist angle between the materials. This approach is promising both for controlling the interactions between the TMDs and for engineering their electronic band structures, yet direct observation of the changes to the electronic structure introduced with varying twist angle has so far been missing. Here, we probe heterobilayers comprised of single-layer MoS${}_2$ and WS${}_2$ with twist angles of $(2.0\pm 0.5{)}^{\circ }$, $(13.0\pm 0.5{)}^{\circ }$, and $(20.0\pm 0.5{)}^{\circ }$ and investigate the differences in their electronic band structure using micro-focused angle-resolved photoemission spectroscopy. We find strong interlayer hybridization between MoS${}_2$ and WS${}_2$ electronic states at the $\bar{\mathrm{\Gamma }}$-point of the Brillouin zone, leading to a transition from a direct bandgap in the single-layer to an indirect gap in the heterostructure. Replicas of the hybridized states are observed at the centre of twist angle-dependent moiré mini Brillouin zones. We confirm that these replica features arise from the inherent moiré potential by comparing our experimental observations with density functional theory calculations of the superlattice dispersion. Our direct visualization of these features underscores the potential of using twisted heterobilayer semiconductors to engineer hybrid electronic states and superlattices that alter the electronic and optical properties of 2D heterostructures.

arXiv comment31 pages, 6 figures in the main text and 5 figures in the supporting information

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Cited by in corpus (4)

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• Ultrafast dynamics of bright and dark excitons in monolayer WSe${}_2$ and heterobilayer WSe${}_2$/MoS${}_2$
• One-dimensional electronic states in a natural misfit structure
• Designer three-dimensional electronic bands in asymmetric transition metal dichalcogenide heterostructures