Non-Magnetic Fractionally Quantized Conductance in Quasi-One Dimensional Semiconductor Structures

ORAL

Abstract

We have investigated quasi-one dimensional carrier transport using holes, (electrons), in Ge-SiGe, (GaAs-AlGaAs), heterostructures in the ballistic regime. At values of carrier concentration below about 5.1010 cm-2 the integer ground state disappears to be replaced by fractional values of conductance. This occurs when the confinement of the carriers is relaxed to be on the verge of two-dimensionality. For holes in Ge we find that, in units of e2/h, the fractional values of conductance are 1/2, spin degenerate, dropping to 1/4 in the presence of a parallel magnetic field and 1/16 which is spin polarized at zero field, (1). The accuracy of the quantization was 0.5%, possibly corresponding to fractional charges of e/2 and e/4.
For electrons in GaAs we find a rich structure, the dominant fractional values of conductance, consistently observed, are in the presence of a weak, asymmetric confinement. The values found are 2/5, 1/2 and 1/6. In the presence of a parallel magnetic field a number of other fractions started to appear, (2). These results will be discussed in relation to the formation of a zig-zag electron configuration with strong interactions between the two rows.
1.Y.Gul et al, J.Phys. Cond. Matt. 30, 09LT01, 2018
2. S. Kumar et al, to be published

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Presenters

  • Michael Pepper

    University College London

Authors

  • Michael Pepper

    University College London

  • Sanjeev Kumar

    University College London

  • Yilmaz Gul

    University College London

  • Maksym Myronov

    Physics, University of Warwick

  • David A Ritchie

    University of Cambridge, Department of Physics, University of Cambridge, Semiconductor Physics, University of Cambridge, Physics, University of Cambridge, Department of Physics, Cavendish Laboratory, Physics, Cambridge University

  • Ian Farrer

    University of Sheffield, Department of Physics, University of Cambridge, Electronic and Electrical Engineering, University of Sheffield, Electrical Engineering, University of Sheffield, Department of Electronic and Electrical Engineering, University of Sheffield, Physics, Sheffield University

  • Henry Montagu

    University College London