Evidence of gate-tunable topological excitations in two-dimensional electron system

ORAL

Abstract

We report experimental observation of a new mechanism of charge transport in two-dimensional electron systems (2DES) in the presence of strong Coulomb interaction and disorder. We show that at low enough temperature the conductivity tends to zero at a non-zero carrier density, which represents the point of essential singularity in a Berezinskii-Kosterlitz-Thouless (BKT)-like transition. Our experiments with many 2DESs in GaAs/AlGaAs heterostructures suggest the charge transport at low carrier densities to be due to the melting of an underlying ordered ground state through proliferation of topological defects. Independent measurement of low-frequency conductivity noise supports this scenario. \\[4pt] [1] R. Koushik\textit{ et al}., Phys. Rev. B \textbf{83}, 085302 (2011) \\[0pt] [2] M. Baenninger\textit{ et al}., Phys. Rev. Lett. \textbf{100}, 016805 (2008).

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Authors

  • R. Koushik

    Department of Physics, Indian Institute of Science, Bangalore

  • Matthias Baenninger

    Cavendish Laboratory, University of Cambridge, J.J.Thomson Avenue, Cambridge; UK

  • Vijay Narayan

    Cavendish Laboratory, University of Cambridge, J.J.Thomson Avenue, Cambridge; UK

  • Subroto Mukerjee

    Department of Physics, Indian Institute of Science, Bangalore

  • Michael Pepper

    Department of Electronic and Electrical Engineering, University College London, Torrington Place, London

  • Ian Farrer

    Cavendish Laboratory, University of Cambridge, J.J.Thomson Avenue, Cambridge; UK, Cavendish Laboratory, University of Cambridge, Cavendish Laboratory, Cambridge University, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK, University of Cambridge

  • Dave Ritchie

    Cavendish Laboratory, University of Cambridge, J.J.Thomson Avenue, Cambridge; UK, Cavendish Laboratory, University of Cambridge, Cavendish Laboratory, Cambridge University, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK, University of Cambridge

  • Arindam Ghosh

    Indian Institute of Science, Bangalore, Department of Physics, Indian Institute of Science, Bangalore, Department of Physics, Indian Institute of Science