In this paper we present an experiment where we measured the quantum coherence of a quasiparticle injected at a well-defined energy above the Fermi sea into the edge states of the integer quantum Hall regime. Electrons are introduced in an electronic Mach-Zehnder interferometer after passing through a quantum dot that plays the role of an energy filter. Measurements show that above a threshold injection energy, the visibility of the quantum interferences is almost independent of the energy. This is true even for high energies, up to 130~μeV, well above the thermal energy of the measured sample. This result is in strong contradiction with our theoretical predictions, which instead predict a continuous decrease of the interference visibility with increasing energy. This experiment raises serious questions concerning the understanding of excitations in the integer quantum Hall regime.
@article{arxiv.1503.05057,
title = {Robust quantum coherence above the Fermi sea},
author = {S. Tewari and P. Roulleau and C. Grenier and F. Portier and A. Cavanna and U. Gennser and D. Mailly and P. Roche},
journal= {arXiv preprint arXiv:1503.05057},
year = {2016}
}