Moiré engineering is being intensively investigated as a method to tune the electronic, magnetic and optical properties of twisted van der Waals materials. Advances in moiré engineering stem from the formation of peculiar moiré superlattices at small, specific twist angles. Here we report configurable nanoscale light–matter waves—phonon polaritons—by twisting stacked α-phase molybdenum trioxide (α-MoO3) slabs over a broad range of twist angles from 0° to 90°. Our combined experimental and theoretical results reveal a variety of polariton wavefront geometries and topological transitions as a function of the twist angle. In contrast to the origin of the modified electronic band structure in moiré superlattices, the polariton twisting configuration is attributed to the electromagnetic interaction of highly anisotropic hyperbolic polaritons in stacked α-MoO3 slabs. These results indicate twisted α-MoO3 to be a promising platform for nanophotonic devices with tunable functionalities.
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All other data that support the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.
The custom code employed in this work to perform all calculations is available from the corresponding author upon reasonable request.
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We acknowledge helpful discussions with X. Jiang, J. Lin and T. Low. Work at Auburn University was supported by the Auburn University Intramural Grants Program and National Science Foundation under grant no. DMR-2005194. Work in P.J.-H.’s group was supported through AFOSR grant FA9550-16-1-0382 (fabrication), and the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant GBMF4541 to P.J.-H. This work made use of the Materials Research Science and Engineering Center Shared Experimental Facilities supported by the National Science Foundation (NSF) (grant number DMR-0819762). The work at Zhejiang University was sponsored by the National Natural Science Foundation of China (NNSFC) under grant numbers 61625502, 11961141010 and 61975176, the Top-Notch Young Talents Program of China, and the Fundamental Research Funds for the Central Universities.
The authors declare no competing interests.
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Chen, M., Lin, X., Dinh, T.H. et al. Configurable phonon polaritons in twisted α-MoO3. Nat. Mater. 19, 1307–1311 (2020). https://doi.org/10.1038/s41563-020-0732-6
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