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Séminaire matériaux 2D et confinement de l’INSP

Ballistic electrons splashing down in a Fermi sea - François Parmentier - Mardi 11 février 2020

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 22-32, 2e étage, salle 201

François Parmentier - Chargé de Recherche au CNRS - Service de Physique de l’état Condensée - CEA Saclay - Groupe Nanoélectronique

Abstract

Understanding how electrons travel in a quantum circuit is one of the main goals of mesoscopic physics. This is particularly crucial in systems in which electronic interactions are exacerbated. For instance, electrostatic interactions between nearby one-dimensional edge channels of the quantum Hall effect have been shown to play a much more important role than what can be naively thought. Indeed, the excitations of the apparently simple system formed by two co-propagating edge channels determined by interactions, which ends up limiting the quantum coherence of electrons traveling in such a system. A seemingly straightforward question has remained unanswered : if one injects an electron at a well-defined energy in an edge channel, and lets it propagate in presence of a nearby edge channel, does it lose energy because of interactions, and can one still detect it after propagation ?

We have directly addressed this fundamental question by performing an energy resolved injection and detection of electrons in a quantum Hall edge channel. We observe for the first time in this system the presence of electrons remaining at finite energy after propagation, and show that their population is strongly suppressed as one increases either their energy, or the propagation length. At sub-microns length, we observe a remarkable revival of finite energy electrons, which corresponds to the recombination of excitations that have split between the two edge channels.

Our findings give us a better understanding of the role of interactions in quantum Hall edge channels, as well as methods to harness them. More complex experiments mimicking quantum optics with electrons can now be envisioned.