Ergodic vs diffusive decoherence in mesoscopic devices

Thibaut Capron ¹, ², Christophe Texier ³, ⁴, 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