Observation of a Fifth of the Electron Charge

 M. Reznikova, R. de Picciottob, T. G. Griffiths, M. Heiblum, and V. Umansky

Braun Center for Submicron Research, Dept. of Cond. Matter Physics,
Weizmann Institute of Science, Rehovot 76100, Israel

The fractional quantum Hall (FQH) effect is a phenomenon observed in the conduction properties of a two-dimensional electron gas subjected to a strong perpendicular magnetic field. The effect results from the strong interaction among electrons, brought about by the high magnetic field, giving rise to fractionally charged quasi-particles that carry the current1-5. These newly imerging quasi-particles can be viewed as nearly non-interacting particles. Here we report the observation of quasi-particles with charge q=e/5, detected by shot noise measurements at filling factor 2/5, namely for a conductance (2/5)g0 (with g0 the quantum conductance). Previous measurements showed that the current is carried by quasi-particles with charge q=e/3, for a conductance g0/3, however, it could be claimed that these measurements were no more than an indirect measurements of the conductance and not the fractional charge. The new results, which are described bellow, demonstrate that quasi-particles with charge q=e/5 carry the current in the n=2/5 fractional Quantum Hall State, validating the existence of fractional charges.

      1. Prange, R. E. and Girvin, S. M. (eds) The Quantum Hall Effect, Springer-Verlag, New York, 1987.
      2. Laughlin, R. B., "Anomalous Quantum Hall Effect: An Incompressible Quantum Fluid with Fractional Charge Excitations", Phys. Rev. Lett., 50, 1395-98 (1983).
      3. Laughlin, R. B., Surf. Sci. 142, 163 (1984).
      4. de-Picciotto, R., Reznikov, M., Heiblum, M., Umansky, V., Bunin, G. and Mahalu D., "Dirrect observation of a fractional charge", Nature 389, 162 (1997).
      5. Saminadayar, L., Glattli D. C., Jin, Y. and Etienne, B., "Observation of the e/3 fractionally charged Laughlin quasiparticles", Phys. Rev. Lett. 79, 2526-2529 (1997).


    a Currently at Physics Department, Technion, Haifa 32000, Israel
    b Currently at Bell-Labs, Lucent Technologies, Murray Hill, NJ, 07974, US.   rd25@lucent.com