Ergodic vs diffusive decoherence in mesoscopic devices

Thibaut Capron 12, Christophe Texier 34, Gilles Montambaux 4, Dominique Mailly 5, Andreas D. Wieck 6, Christopher Bäuerle 1, Laurent Saminadayar 1

Physical Review B (Condensed Matter) 87, 4 (2013) 041307

We report on the measurement of phase coherence length in a high mobility two-dimensional electron gas patterned in two different geometries, a wire and a ring. The phase coherence length is extracted both from the weak localization correction in long wires and from the amplitude of the Aharonov-Bohm oscillations in a single ring, in a low temperature regime when decoherence is dominated by electronic interactions. We show that these two measurements lead to different phase coherence lengths, namely $L_{\Phi}^\mathrm{wire}\propto T^{-1/3}$ and $L_{\Phi}^\mathrm{ring}\propto T^{-1/2}$. This difference reflects the fact that the electrons winding around the ring necessarily explore the whole sample (ergodic trajectories), while in a long wire the electrons lose their phase coherence before reaching the edges of the sample (diffusive regime).

  • 1 : Institut Néel (NEEL)
    CNRS : UPR2940 – Université Joseph Fourier - Grenoble I – Institut National Polytechnique de Grenoble (INPG)
  • 2 : Université de Grenoble
    Université Joseph Fourier - Grenoble I – Université Stendhal - Grenoble III – Université Pierre-Mendès-France - Grenoble II
  • 3 : Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS)
    CNRS : UMR8626 – Université Paris XI - Paris Sud
  • 4 : Laboratoire de Physique des Solides (LPS)
    CNRS : UMR8502 – Université Paris XI - Paris Sud
  • 5 : Laboratoire de photonique et de nanostructures (LPN)
    CNRS : UPR20
  • 6 : Lehrstuhl für Angewandte Festkörperphysik
    Lehrstuhl für Angewandte Festkörperphysik