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Résumé |
In 1D conductors interactions are enhanced by the confinement, which can have spectacular consequences such as the separation of the spin and charge degrees of freedom. A prototypal ballistic 1D conductors is realized by the edge channels of the integer quantum Hall regime, along which the current propagate without dissipation. However, interactions effects are usually hidden by the robustness of Hall currents. It is only in novel electron quantum optics experiments using edge states (see e.g. the pioneer work [1]) that striking phenomena were attributed to the presence of interactions.
In order to probe interactions, we have driven an edge channel out-of-equilibrium and observed its relaxation toward equilibrium. The energy relaxation is characterized precisely by measuring the energy distribution f(E) of the electronic edge states. This can be done using the discrete electronic levels in a quantum dot as energy filters [2]. We then monitored the deformation of f(E) along the edge path, which results from the energy exchanges taking place. This provides information on the inelastic mechanisms and also on the nature of the electronic edge states.
The experiment was performed at filling factor two, where two adjacent channels propagate along the edge [3]. Whereas there are no discernable energy transfers towards thermalized states, we find an efficient energy redistribution between the two channels, without particle exchanges. The observed short energy relaxation length challenges the usual description of quantum Hall excitations as quasiparticles localized in one edge channel [3,4]. Yet, we found that it is possible to efficiently freeze the energy exchanges rate, and thereby to increase the quantum coherence length, with adequate geometries [5].
[1] Y. Ji et al., Nature 422, 415 (2003)
[2] C. Altimiras et al., Nature phys. 6, 34 (2010)
[3] H. le Sueur et al., Phys. Rev. Lett. 105, 056803 (2010)
[4] P. Degiovanni et al. Phys. Rev. B 81, 121302(R) (2010)
[5] C. Altimiras et al., Phys. Rev. Lett. 105, 226804 (2010) |
