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Excitons in semiconductor moiré superlattices

Nature Nanotechnology volume 17, pages 227–238 (2022)Cite this article

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Abstract

Semiconductor moiré superlattices represent a rapidly developing area of engineered photonic materials and a new platform to explore correlated electron states and quantum simulation. In this Review, we briefly introduce early experiments that identified new exciton resonances in transition metal dichalcogenide heterobilayers and discuss several topics including two types of transition metal dichalcogenide moiré superlattice, new optical selection rules, early evidence of moiré excitons, and how the resonant energy, dynamics and diffusion properties of moiré excitons can be controlled via the twist angle. To interpret optical spectra, it is important to measure the energy modulation within a moiré supercell. In this context, we describe a few scanning tunnelling microscopy experiments that measure the moiré potential landscape directly. Finally, we review a few recent experiments that applied excitonic optical spectroscopy to probe correlated electron phenomena in transition metal dichalcogenide moiré superlattices.

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Fig. 1: Excitons and MSLs in TMD heterobilayers.
Fig. 2: Unveiling the moiré local bandgap and flat bands via STM/S.
Fig. 3: Initial experimental evidence of moiré excitons.
Fig. 4: Dynamics of moiré excitons.
Fig. 5: Spatial diffusion of moiré excitons.
Fig. 6: Experimental evidence of the correlated electron states probed by excitons.

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Acknowledgements

D.H. and X.L. gratefully acknowledge financial support from the Department of Energy, Basic Energy Science program via grant DE-SC0019398. C.-K.S. and X.L. are partially supported by NSF MRSEC under Cooperative Agreement No. DMR-1720595. J.C. and X.L. acknowledge financial support from NSF DMR-1808042 and the Welch Foundation F-1662. C.-K.S. acknowledges financial support from the Welch Foundation via F-1672.

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Authors and Affiliations

  1. Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA

    Di Huang, Junho Choi, Chih-Kang Shih & Xiaoqin Li

  2. Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA

    Junho Choi, Chih-Kang Shih & Xiaoqin Li

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  1. Di Huang
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Huang, D., Choi, J., Shih, CK. et al. Excitons in semiconductor moiré superlattices. Nat. Nanotechnol. 17, 227–238 (2022). https://doi.org/10.1038/s41565-021-01068-y

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