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Observation of a quarter of an electron charge at the ν = 5/2 quantum Hall state

Nature volume 452, pages 829–834 (2008)Cite this article

Abstract

The fractional quantum Hall effect, where plateaus in the Hall resistance at values of h/ν e2 coexist with zeros in the longitudinal resistance, results from electron correlations in two dimensions under a strong magnetic field. (Here h is Planck’s constant, ν the filling factor and e the electron charge.) Current flows along the sample edges and is carried by charged excitations (quasiparticles) whose charge is a fraction of the electron charge. Although earlier research concentrated on odd denominator fractional values of ν, the observation of the even denominator ν = 5/2 state sparked much interest. This state is conjectured to be characterized by quasiparticles of charge e/4, whose statistics are ‘non-abelian’—in other words, interchanging two quasiparticles may modify the state of the system into a different one, rather than just adding a phase as is the case for fermions or bosons. As such, these quasiparticles may be useful for the construction of a topological quantum computer. Here we report data on shot noise generated by partitioning edge currents in the ν = 5/2 state, consistent with the charge of the quasiparticle being e/4, and inconsistent with other possible values, such as e/2 and e. Although this finding does not prove the non-abelian nature of the ν = 5/2 state, it is the first step towards a full understanding of these new fractional charges.

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Figure 1: Quantum Hall effect in the second Landau level.
Figure 2: The procedure used to identify lower lying states within the QPC.
Figure 3: Conductance and shot noise measurements of partitioned particles at the 5/2 state.
Figure 4: Conductance and shot noise measurements of partitioned particles at the 5/2 state, with a filling factor in the bulk of ν B = 5/2.
Figure 5: Conductance and shot noise at different filling factors in the QPC.

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Acknowledgements

We thank A. Ra’anan for laying the foundations for these experiments; A. Schreier, I. Neder, N. Ofek, Y. Gross, E. Grosfeld, Y. Gefen, B. I. Halperin, Y. Levinson, B. Rosenow and S. Das Sarma for their suggestions and assistance; J. Miller and C. Marcus for sharing with us their experience of the fabrication process; and L. Pfeiffer for providing us with a sample for initial experimentation. M.H. acknowledges partial support from the Israeli Science Foundation (ISF), the German Israeli Foundation (GIF), and the Minerva foundation. A.S. acknowledges support from the US-Israel Bi-national Science Foundation, the Minerva foundation, and the ISF.

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  1. Department of Condensed Matter Physics, Braun Center for Submicron Research, Weizmann Institute of Science, Rehovot 76100, Israel

    M. Dolev, M. Heiblum, V. Umansky, Ady Stern & D. Mahalu

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  1. M. Dolev
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Correspondence to M. Dolev.

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Dolev, M., Heiblum, M., Umansky, V. et al. Observation of a quarter of an electron charge at the ν = 5/2 quantum Hall state. Nature 452, 829–834 (2008). https://doi.org/10.1038/nature06855

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