0.7 Anomaly, Spin-Mixing and Emergent Spin Gap in Quantum Point Contacts with Strong Spin-Orbit Interaction

ORAL

Abstract

Quantum point contacts (QPCs) are 1D charge constrictions where ballistic conductance through the channel is quantised in integer units, with the exception of the 0.7(2e2/h) anomaly. The microscopic origin of the 0.7 anomaly remains contentious after over 20 years of study, and the additional influence of spin-orbit interaction (SOI) is even more poorly understood.
Here we characterise the 0.7 anomaly for 1D holes with strong interactions and strong SOI. Similarly to electrons, the 0.7 anomaly in 1D holes shares the signature behaviour of evolving to 0.5(2e2/h) in applied magnetic field. However, while the electron 0.7 anomaly isotropically Zeeman spin-splits in magnetic field, the hole 0.7 anomaly exhibits a weak anistropic response in in-plane magnetic field. We show the magnetic field orientation dependence of the first 1D hole subband, and demonstrate a new and robust signature for the opening of a spin gap. We compare our measurements to recent theory where the Rashba SOI term predicts the correct anisotropy of the Zeeman spin-splitting in the first hole subband as well as the opening of a spin gap in magnetic field. The opening of a spin gap in 1D hole semiconducting systems has significant implications for the formation of helical spin gaps and Majorana excitations.

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Presenters

  • Karina Hudson

    Univ of New South Wales

Authors

  • Karina Hudson

    Univ of New South Wales

  • Ashwin Srinivasan

    Univ of New South Wales

  • Olga Goulko

    Physics, Boise State University, Boise State University

  • Jarrod Adam

    Univ of New South Wales

  • Qingwen WANG

    School of Physics, University of New South Wales, Univ of New South Wales

  • LaReine Yeoh

    Univ of New South Wales

  • Oleh Klochan

    Univ of New South Wales, School of Physics, University of New South Wales

  • 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

  • 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

  • Jan Von Delft

    Arnold Sommerfeld Centre for Theoretical Physics, Ludwig-Maximilians University, Ludwig-Maximilians-Universität München, Munich, Germany, University of Munich, Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-University of Munich, Germany

  • Alex R Hamilton

    School of Physics, University of New South Wales, Univ of New South Wales, University of New South Wales