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Observation of a G = ½ e<sup>2</sup>/h quantized conductance plateau in a quantum point contact at the v = 2/3 fractional quantum Hall state

ORAL

Abstract

Quantum point contacts (QPCs) can be used to reflect quantum Hall edge states and probe the properties of fractional quasiparticles. We have investigated the v = 2/3 state in QPCs on a GaAs/AlGaAs heterostructure designed to achieve sharp confinement. When measuring conductance as a function of gate voltage and applying a small finite bias, we observe an intermediate conductance plateau with G = ½ e2/h. This plateau is a robust feature, being observed in multiple QPCs, and exists over a significant range of magnetic field, gate voltage, and source-drain bias. Using a simple model which considers scattering and equilibration between counterpropagating edge modes, we have found that this half-integer plateau is consistent with full reflection of an inner counterpropagating -1/3 edge mode while the outer integer mode is fully transmitted. In a QPC fabricated on a standard structure which is expected to have a soft confining potential, we instead observe an intermediate plateau at G = 1/3 e2/h, which is consistent with a theoretically predicted transition to an edge reconstructed state when the confining potential becomes soft.

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Presenters

  • Michael J Manfra

    Purdue University, Microsoft Quantum Purdue, Purdue University, Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA; Microsoft Quantum Lab, Purdue University, West Lafayette, IN, USA, Physics and Astronomy, Purdue University, Department of Physics and Astronomy, Birck Nanotechnology Center, School of Electrical and Computer Engineering and Microsoft Quantum Lab West Lafayette, Purdue University, Department of Physics and Astronomy and Nanotechnology Center Purdue University, Microsoft Quantum Lab West Lafayette, Department of Physics and Astronomy, Birck Nanotechnology Center, School of Materials Engineering and School of Electrical and Computer Engineering, Purdue University

Authors

  • James R Nakamura

    Purdue University

  • Shuang Liang

    Purdue University

  • Geoffrey C Gardner

    Purdue University

  • Michael J Manfra

    Purdue University, Microsoft Quantum Purdue, Purdue University, Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA; Microsoft Quantum Lab, Purdue University, West Lafayette, IN, USA, Physics and Astronomy, Purdue University, Department of Physics and Astronomy, Birck Nanotechnology Center, School of Electrical and Computer Engineering and Microsoft Quantum Lab West Lafayette, Purdue University, Department of Physics and Astronomy and Nanotechnology Center Purdue University, Microsoft Quantum Lab West Lafayette, Department of Physics and Astronomy, Birck Nanotechnology Center, School of Materials Engineering and School of Electrical and Computer Engineering, Purdue University