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Even-denominator fractional quantum Hall physics in ZnO


The fractional quantum Hall (FQH) effect emerges in high-quality two-dimensional electron systems exposed to a magnetic field when the Landau-level filling factor, νe, takes on a rational value. Although the overwhelming majority of FQH states have odd-denominator fillings, the physical properties of the rare and fragile even-denominator states are most tantalizing in view of their potential relevance for topological quantum computation. For decades, GaAs has been the preferred host for studying these even-denominator states, where they occur at νe = 5/2 and 7/2. Here we report an anomalous series of quantized even-denominator FQH states outside the realm of III–V semiconductors in the MgZnO/ZnO 2DES electron at νe = 3/2 and 7/2, with precursor features at 9/2; all while the 5/2 state is absent. The effect in this material occurs concomitantly with tunability of the orbital character of electrons at the chemical potential, thereby realizing a new experimental means for investigating these exotic ground states.

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Figure 1: Base temperature (T < 20 mK) magnetotransport data recorded on the MgZnO/ZnO heterostructure.
Figure 2: Energy level sequence and magnetotransport map with sample rotation.
Figure 3: Tilt angle dependence of the resistance and activation energy at prominent FQH states.
Figure 4: Base temperature transport mapping with sample rotation around νe = 3/2.


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We thank K. v. Klitzing, T. Arima, R. Morf, M. Shayegan, Y. Liu and V. Scarola for discussions. This work was partly supported by Grant-in-Aids for Scientific Research (S) No. 24226002 from MEXT, Japan, ‘Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST)’ Program from the Japan Society for the Promotion of Science (JSPS) initiated by the Council for Science and Technology Policy and the German Ministry of Science and Education (BMBF). J.F. acknowledges the support of the Marubun Research Promotion Foundation.

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J.F. grew the heterostructure. J.F., B.F. and D.Z. performed the low-temperature measurements. J.F. analysed the data. J.F. and J.H.S. wrote the manuscript with input from all authors. All authors discussed the results and planned the experiments with J.F., D.M., Y.K., A.T. and M.K. initiating the project.

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Correspondence to J. H. Smet or M. Kawasaki.

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The authors declare no competing financial interests.

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Falson, J., Maryenko, D., Friess, B. et al. Even-denominator fractional quantum Hall physics in ZnO. Nature Phys 11, 347–351 (2015).

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