Structural and Electronic Evolution in Sub-Degree to Few-Degree Twisted 2D Moiré Superlattices
ORAL
Abstract
Tuning the interlayer twist angle in bilayer graphene and transition metal dichalcogenides enables the realization of moiré superlattices with tunable periodicity. These twisted structures exhibit remarkable electronic properties originating from low-energy flat bands and complex atomic and lattice reconstructions. Following the discovery of strongly correlated insulating and superconducting states in systems such as twisted bilayer graphene (TBG) and twisted bilayer WSe₂ (TBWSe₂), moiré superlattices have garnered extensive attention as a versatile platform for studying emergent quantum phenomena.
At low twist angles, TBG and TBWSe₂ undergo pronounced lattice reconstruction, which locally alters atomic registry and significantly influences their electronic characteristics. In TBG, incommensurate moiré patterns evolve into commensurate domains below θ ≈ 2°, featuring enlarged AB/BA-stacked regions and reduced AA regions that form a triangular network of domain walls (DWs). Despite considerable theoretical and experimental progress, systematic investigations correlating lattice reconstruction with mechanical and electronic evolution across sub-degree to few-degree twist angles remain limited. Understanding atomic reconstruction at van der Waals interfaces offers a promising route for engineering and controlling moiré superlattice properties.
In this work, we investigate the lattice reconstruction in TBG and TBWSe₂ across sub-degree to low twist angles. Using piezoresponse force microscopy under ambient conditions, we characterize the moiré periodicity and local lattice relaxation. We reveal how the periodicity of relaxed moiré superlattices scales with twist angle and elastic properties. While moderate twist angles produce a triangular DW network, sub-degree twists give rise to one-dimensional channels along DWs in TBG. Furthermore, we probe the local electronic properties of these moiré systems by fabricating transport devices at precisely defined regions, offering new insights into the interplay between lattice reconstruction and emergent electronic behavior.
At low twist angles, TBG and TBWSe₂ undergo pronounced lattice reconstruction, which locally alters atomic registry and significantly influences their electronic characteristics. In TBG, incommensurate moiré patterns evolve into commensurate domains below θ ≈ 2°, featuring enlarged AB/BA-stacked regions and reduced AA regions that form a triangular network of domain walls (DWs). Despite considerable theoretical and experimental progress, systematic investigations correlating lattice reconstruction with mechanical and electronic evolution across sub-degree to few-degree twist angles remain limited. Understanding atomic reconstruction at van der Waals interfaces offers a promising route for engineering and controlling moiré superlattice properties.
In this work, we investigate the lattice reconstruction in TBG and TBWSe₂ across sub-degree to low twist angles. Using piezoresponse force microscopy under ambient conditions, we characterize the moiré periodicity and local lattice relaxation. We reveal how the periodicity of relaxed moiré superlattices scales with twist angle and elastic properties. While moderate twist angles produce a triangular DW network, sub-degree twists give rise to one-dimensional channels along DWs in TBG. Furthermore, we probe the local electronic properties of these moiré systems by fabricating transport devices at precisely defined regions, offering new insights into the interplay between lattice reconstruction and emergent electronic behavior.
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Presenters
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Mukesh Kumar Das
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore