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Coherent bunching of anyons and dissociation in an interference experiment

Nature volume 642, pages 922–927 (2025)Cite this article

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Abstract

Aharonov–Bohm interference of fractional quasiparticles in the quantum Hall effect generally reveals their elementary charge (e*)1,2,3,4,5,6,7,8,9,10,11,12,13,14,15. Recently, our interferometry experiments with several ‘particle states’ reported flux periods of ΔΦ = (e/e*)Φ0 (with Φ0 the flux quantum) at moderate temperatures16. Here we report interference measurements of ‘particle–hole conjugated’ states at filling factors ν = 2/3, 3/5 and 4/7, which revealed unexpected flux periodicities of ΔΦ = ν−1Φ0. The measured shot-noise Fano factor (F) of the partitioned quasiparticles in each of the quantum point contacts of the interferometer was F = ν (ref. 17) rather than that of the elementary charge F = e*/e (refs. 18,19). These observations indicate that the interference of bunched (clustered) elementary quasiparticles occurred for coherent pairs, triples and quadruplets, respectively. A small metallic gate (top gate), deposited in the centre of the interferometer bulk, formed an antidot (or a dot) when charged, thus introducing local quasiparticles at the perimeter of the (anti)dot. Surprisingly, such charging led to a dissociation of the ‘bunched quasiparticles’ and, thus, recovered the conventional flux periodicity set by the elementary charge of the quasiparticles. However, the shot-noise Fano factor (of each quantum point contact) consistently remained at F = ν, possibly due to the neutral modes accompanying the conjugated states. The two observations—bunching and debunching (or dissociation)—were not expected by current theories. Similar effects may arise in Jain’s ‘particle states’ (at lower temperatures) and at even denominator fractional quantum Hall states20.

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Fig. 1: Device structure of an OMZI.
Fig. 2: Shot noise measured in a single QPC of the OMZI.
Fig. 3: Evidence of coherent bunching of anyons in particle–hole conjugated states.
Fig. 4: Evidence of coherent dissociation of bunched anyons in particle–hole conjugated states.
Fig. 5: Evolution of the dissociated anyons on charging the top gate for νb = 2/3 and 3/5.

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Data availability

The data that support the plots within this paper and other findings of this study are publicly available at https://doi.org/10.5281/zenodo.15395283 (ref. 39). Source data are provided with this paper.

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Acknowledgements

M.H. thanks Y. Ronen for fruitful discussions. D.F.M. acknowledges many illuminating conversations on quantum Hall interferometry with Y. Ronen. B.G. thanks A. K. Paul for his helpful comment that improved the device. M.L. thanks the Ariane de Rothschild Women Doctoral Program for their support. D.F.M. acknowledges the support of the Israel Science Foundation (Grant No. 2572/21) and the Deutsche Forschungsgemeinschaft (DFG) within the CRC network TR 183 (Project Grant No. 277101999). M.H. acknowledges the support of the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 833078) and the support of the Israel Science Foundation (Grant No. 1510/22).

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Authors and Affiliations

  1. Braun Center for Sub-Micron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel

    Bikash Ghosh, Maria Labendik, Vladimir Umansky & Moty Heiblum

  2. Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel

    David F. Mross

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  1. Bikash Ghosh
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  2. Maria Labendik
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  3. Vladimir Umansky
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  4. Moty Heiblum
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Contributions

B.G. fabricated the devices. B.G. and M.L. performed the measurements and analysed the data with the input from M.H. M.H. supervised the design, execution and data analysis in the experiment. D.F.M. worked on the theoretical aspects and data analysis. V.U. grew the GaAs heterostructures. All authors contributed to the writing of the manuscript.

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Correspondence to Moty Heiblum.

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Supplementary Notes, methods, Figs. 1–11 and references.

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Ghosh, B., Labendik, M., Umansky, V. et al. Coherent bunching of anyons and dissociation in an interference experiment. Nature 642, 922–927 (2025). https://doi.org/10.1038/s41586-025-09143-3

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