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  • Review Article
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Emerging exciton physics in transition metal dichalcogenide heterobilayers

Nature Reviews Materials volume 7, pages 778–795 (2022)Cite this article

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Abstract

Atomically thin transition metal dichalcogenides (TMDs) are 2D semiconductors with tightly bound excitons and correspondingly strong light–matter interactions. Owing to the weak van der Waals bonding between layers, TMDs can be isolated and stacked together to form synthetic heterostructures with emergent electronic and excitonic properties. In this Review, we focus on the emergent exciton physics in moiré superlattices and in TMD heterobilayers coupled to optical cavities, where exciton behaviour can be dramatically modified by the environment. In moiré superlattices, a small twist angle or lattice mismatch between the layers introduces a periodic variation in the interlayer alignment that leads to exciton localization, modified optical selection rules and strong correlations. In cavity–heterostructure systems, light–matter interaction is enhanced and exciton states can couple to the cavity to form exciton-polaritons, whose properties depend on the specific TMD layers involved and their alignment. Here, we discuss recent theoretical and experimental progress towards realizing exotic exciton states in TMD heterobilayers and comment on future scientific and technological directions.

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Fig. 1: Excitons in TMD heterostructures.
Fig. 2: Transition metal dichalcogenide moiré superlattices.
Fig. 3: Intralayer moiré excitons.
Fig. 4: Interlayer moiré excitons.
Fig. 5: Hybrid moiré excitons.
Fig. 6: Excitonic probes of correlations in moiré superlattices.
Fig. 7: Excitons in optical cavities.
Fig. 8: Exciton reservoirs in TMD heterostructures.

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Acknowledgements

E.Y.P., Y.Z., L.Z., J.Z., A.H.M., H.D. and F.W. acknowledge support from the US Army Research Office under MURI award W911NF-17-1-0312. E.Y.P., L.Z. and H.D. were also supported by the Air Force Office of Scientific Research under award FA2386-18-1-4086 and the National Science Foundation under award DMR 1838412. D.W. was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under contract number DE-AC02-05-CH11231 (van der Waals heterostructures programme, KCWF16). E.C.R. acknowledges support from the Department of Defense through the National Defense Science and Engineering Graduate (NDSEG) fellowship programme.

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Authors and Affiliations

  1. Department of Physics, University of California at Berkeley, Berkeley, CA, USA

    Emma C. Regan, Danqing Wang & Feng Wang

  2. Graduate Group in Applied Science and Technology, University of California at Berkeley, Berkeley, CA, USA

    Emma C. Regan & Danqing Wang

  3. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Emma C. Regan, Danqing Wang & Feng Wang

  4. Department of Physics, University of Michigan, Ann Arbor, MI, USA

    Eunice Y. Paik, Long Zhang & Hui Deng

  5. Department of Physics, University of Texas at Austin, Austin, TX, USA

    Yongxin Zeng, Jihang Zhu & Allan H. MacDonald

  6. Kavli Energy NanoScience Institute at University of California, Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Feng Wang

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Regan, E.C., Wang, D., Paik, E.Y. et al. Emerging exciton physics in transition metal dichalcogenide heterobilayers. Nat Rev Mater 7, 778–795 (2022). https://doi.org/10.1038/s41578-022-00440-1

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