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Imaging electronic transport at the nanoscale.

NAPS

UCL Promoteurs : Benoît  Hackens and Vincent Bayot

UCL Collaborators : Damien Cabosart, Frederico Rodrigues Martins, Sébastien Faniel, Cristiane Nascimento Santos,
     Sorin Melinte (ICTEAM)

External Collaborators : Mansour Shayegan (Princeton Univ.), Xavier Wallart (IEMN, Villeneuve d’Ascq),
   Serge Huant and Hermann Sellier (Institut Néel, Grenoble), Marco Pala (INPG, Grenoble), Bernd Rosenow (U. Leipzig)

Funding : ARC ("Stresstronics"), FSR, FNRS, ANR (France)

imaging BenoitTraditionally, the understanding of quantum transport relied on the measurement of macroscopic properties such as the conductance or the resistance. While powerful when coupled to statistical theories, this approach cannot provide a detailed image of “how electrons behave down there”. Ideally, understanding transport at the nanoscale would require tracking each electron inside the nano-device. Significant progress towards this goal was obtained by combining scanning probe microscopy with transport measurements.
We use this method to probe electron propagation in nano-devices fabricated from semiconductor heterostructures (GaAs/AlGaAs, InGaAs/InAlAs) thanks to the WINFAB infrastructure (UCL), in various regimes of transport, down to extremely low temperature (0.02 K) and high magnetic field (17 T). We managed to prove that coherent and ballistic propagation of electrons can be investigated in situ, and even be controlled by tuning the potential felt by electrons at the nanoscale. Our research currently deals with mapping transport in the Quantum Hall regime (integer and fractional), manipulating quantum Hall localized states, as well as mapping transport in graphene devices.

References :

  • F. Martins, S. Faniel, B. Rosenow, H. Sellier, S. Huant, M. G. Pala, L. Desplanque, X. Wallart, V. Bayot and B. Hackens, Coherent tunneling accross a quantum point contact in the quantum Hall regime, to appear in Nature Scientific Report 3, 1416 (2013).
  • F. Martins, S. Faniel, B. Rosenow, M. G. Pala, H. Sellier, S. Huant, L. Desplanque, X. Wallart, V. Bayot and B. Hackens, Scanning gate spectroscopy of transport accross a quantum Hall nano-island, New Journal of Physics 15, 013049 (2013).
  • M.G. Pala, S. Baltazar, P. Liu, H. Sellier, B. Hackens, F. Martins, V. Bayot, X. Wallart, L. Desplanque and S. Huant, Transport inefficiency in branched-out mesoscopic networks: an analog of the Braess paradox, Phuysical Review Letters 108, 076802 (2012).
  • B. Hackens, F. Martins, S. Faniel, C.A. Dutu, H. Sellier, S. Huant, M. Pala, L. Desplanque, X. Wallart and V. Bayot, Imaging Coulomb islands in a quantum hall interferometer, Nature Communications, 1, 39 (2010)