Exciton condensates (ECs) are macroscopic coherent states arising from condensation of electron–hole pairs1. Bilayer heterostructures, consisting of two-dimensional electron and hole layers separated by a tunnel barrier, provide a versatile platform to realize and study ECs2,3,4. The tunnel barrier suppresses recombination, yielding long-lived excitons5,6,7,8,9,10. However, this separation also reduces interlayer Coulomb interactions, limiting the exciton binding strength. Here, we report the observation of ECs in naturally occurring 2H-stacked bilayer WSe2. In this system, the intrinsic spin–valley structure suppresses interlayer tunnelling even when the separation is reduced to the atomic limit, providing access to a previously unattainable regime of strong interlayer coupling. Using capacitance spectroscopy, we investigate magneto-ECs, formed when partially filled Landau levels couple between the layers. We find that the strong-coupling ECs show dramatically different behaviour compared with previous reports, including an unanticipated variation of EC robustness with the orbital number, and find evidence for a transition between two types of low-energy charged excitations. Our results provide a demonstration of tuning EC properties by varying the constituent single-particle wavefunctions.
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Electrical control of hybrid exciton transport in a van der Waals heterostructure
Nature Photonics Open Access 20 April 2023
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Experimental data relevant to figures in the main text and data of numerical calculations are available at https://doi.org/10.5281/zenodo.6377084. All other raw data are available from the corresponding author upon reasonable request.
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We thank E. Tutuc for helpful discussions and W. Coniglio and B. Pullum for help with experiments at the National High Magnetic Field Lab. This research is primarily supported by the US Department of Energy (DE-SC0016703). Synthesis of WSe2 (D.R., B.K., K.B.) was supported by the Columbia University Materials Science and Engineering Research Center, through National Science Foundation grants DMR-1420634 and DMR-2011738. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation cooperative agreement no. DMR-1157490 and the State of Florida. D.A.A. acknowledges support by the Swiss National Science Foundation and by the European Research Council (grant agreement no. 864597). Z.P. acknowledges support by the Leverhulme Trust Research Leadership Award RL-2019-015. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the Ministry of Education, Culture, Sports, Science and Technology, Japan (grant no. JPMXP0112101001) and Japan Society for the Promotion of Science KAKENHI (grant nos JP19H05790 and JP20H00354).
The authors declare no competing interests.
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Shi, Q., Shih, EM., Rhodes, D. et al. Bilayer WSe2 as a natural platform for interlayer exciton condensates in the strong coupling limit. Nat. Nanotechnol. 17, 577–582 (2022). https://doi.org/10.1038/s41565-022-01104-5
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