Bunching of fractionally charged quasiparticles tunnelling through high-potential barriers

Abstract

Shot noise measurements have been used to measure the charge of quasiparticles in the fractional quantum Hall (FQH) regime1,2,3. To induce shot noise in an otherwise noiseless current of quasiparticles, a barrier is placed in its path to cause weak backscattering. The measured shot noise is proportional to the charge of the quasiparticles; for example, at filling factor v=1/3, noise corresponding to q=e/3 appears. For increasingly opaque barriers, the measured charge increases monotonically, approaching q=e asymptotically4,5. It was therefore believed that only electrons, or alternatively, three bunched quasiparticles, can tunnel through high-potential barriers encountered by a noiseless current of quasiparticles. Here we investigate the interaction of e/3 quasiparticles with a strong barrier in FQH samples and find that bunching of quasiparticles in the strong backscattering limit depends on the average dilution of the quasiparticle current. For a very dilute current, bunching ceases altogether and the transferred charge approaches q=e/3. This surprising result demonstrates that quasiparticles can tunnel individually through high-potential barriers originally thought to be opaque for them.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Schematic and actual representations of the quasiparticle injector followed by a quasiparticle filter, both made of quantum point contacts, QPC1 and QPC2, respectively.
Figure 3: Comparison of the charge characterizing the pinched QPC2 for two extreme cases of the impinging current: not diluted (noiseless) and highly dilute, keeping the same transmitted current.
Figure 2: Noise and transmission measurements of the pinched QPC2 (with transmission t2 ≈ 0.1 at zero bias) for two different values of dilution of the impinging current: t1=0.7 (a) and 0.2 (b).
Figure 4: Evolution of the effective charge q2 that characterizes the pinched QPC2 in response to different values of dilution t1 of the impinging current (extracted from curves similar to that in Fig. 3a).
Figure 5: Dependence of the transmission t2 of the pinched QPC2 on the dilution t1 of the impinging current.

References

  1. 1

    de Picciotto, R. et al. Direct observation of a fractional charge. Nature 389, 162–164 (1997).

    ADS  CAS  Article  Google Scholar 

  2. 2

    Saminadayar, L., Glattli, D. C., Jin, Y., Etienne, B. Observation of the e/3 fractionally charged Laughlin quasiparticle. Phys. Rev. Lett. 79, 2526–2529 (1997).

    ADS  CAS  Article  Google Scholar 

  3. 3

    Reznikov, M., de-Picciotto, R., Griffiths, T. G., Heiblum, M. & Umansky, V. Observation of quasiparticles with one-fifth of an electron's charge. Nature 399, 238–241 (1999).

    ADS  CAS  Article  Google Scholar 

  4. 4

    Kane, C. L. & Fisher, M. P. A. Nonequilibrium noise and fractional charge in the quantum Hall effect. Phys. Rev. Lett. 72, 724–727 (1994).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Griffiths, T. G., Comforti, E., Heiblum, M., Stern, A. & Umansky, V. Evolution of quasiparticle charge in the fractional quantum hall regime. Phys. Rev. Lett. 85, 3918–3921 (2000).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Schottky, W. Über spontane Stromschwankungen in verschieden Elektrizitätsleitern. Ann. Phys. (Leipzig) 57, 541–567 (1918).

    ADS  Article  Google Scholar 

  7. 7

    Prange, R. E. & Girvin, S. M. (eds) The Quantum Hall Effect (Springer, New York, 1987).

    Google Scholar 

  8. 8

    Laughlin, R. B. Anomalous quantum Hall effect: an incompressible quantum fluid with fractional charge excitations. Phys. Rev. Lett. 50, 1395–1398 (1982).

    ADS  Article  Google Scholar 

  9. 9

    Khlus, V. K. Current and voltage fluctuations in microjunctions of normal and superconducting metals. Sov. Phys. JETP 66, 1243–1249 (1987).

    Google Scholar 

  10. 10

    Lesovik, G. B. Excess quantum noise in 2D ballistic point contacts. JETP Lett. 49, 592–594 (1989).

    ADS  Google Scholar 

  11. 11

    Comforti, E., Chung, Y. C., Heiblum, M. & Umansky, V. Multiple scattering of fractionally-charged quasiparticles.Preprint cond-mat/0112367 at 〈http://xxx.lanl.gov〉 (2001).

  12. 12

    Oliver, W. D., Kim, J., Liu, R. C. & Yamamoto, Y. Hanbury Brown and Twiss-type experiment with electrons. Science 284, 299–301 (1999).

    ADS  CAS  Article  Google Scholar 

Download references

Acknowledgements

The work was partly supported by the Israeli Academy of Science and by the German-Israel Foundation (GIF). We thank A. Yacoby, A. Stern and Y. Levinson for discussions.

Author information

Affiliations

Authors

Corresponding author

Correspondence to M. Heiblum.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Comforti, E., Chung, Y., Heiblum, M. et al. Bunching of fractionally charged quasiparticles tunnelling through high-potential barriers. Nature 416, 515–518 (2002). https://doi.org/10.1038/416515a

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Sign up for the Nature Briefing newsletter for a daily update on COVID-19 science.
Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing