New signatures of the spin gap in quantum point contacts

Hudson, K.L. and Srinivasan, A. and Goulko, O. and Adam, J. and Wang, Q. and Yeoh, L.A. and Klochan, O. and Farrer, I. and Ritchie, D.A. and Ludwig, Ar. and Wieck, A.D. and von Delft, J. and Hamilton, A.R.

Volume: 12 Pages:
DOI: 10.1038/s41467-020-19895-3
Published: 2021

One dimensional semiconductor systems with strong spin-orbit interaction are both of fundamental interest and have potential applications to topological quantum computing. Applying a magnetic field can open a spin gap, a pre-requisite for Majorana zero modes. The spin gap is predicted to manifest as a field dependent dip on the first 1D conductance plateau. However, disorder and interaction effects make identifying spin gap signatures challenging. Here we study experimentally and numerically the 1D channel in a series of low disorder p-type GaAs quantum point contacts, where spin-orbit and hole-hole interactions are strong. We demonstrate an alternative signature for probing spin gaps, which is insensitive to disorder, based on the linear and non-linear response to the orientation of the applied magnetic field, and extract a spin-orbit gap ΔE ≈ 500 μeV. This approach could enable one-dimensional hole systems to be developed as a scalable and reproducible platform for topological quantum applications. © 2021, The Author(s).

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