• Séminaire nano-électronique quantique
• Personne à contacter : Robert Whitney ()
• Lieu : Salle Rémy Lemaire K223, Institut Néel

Résumé :

In my seminar, I will discuss measurements of low and high frequency noise in quantum Hall conductors and how they can probe the elementary excitations propagating along the edge channels in the integer and fractional cases.

I will first present how low frequency noise measurements can be used to extract the electronic states propagating along the edge channels of the integer quantum Hall regime. Combining two-electron Hong-Ou-Mandel interferometry [1] with signal processing techniques, we have implemented a quantum tomography protocol [2,3] able of extracting from any electrical current the generated electron and hole wavefunctions as well as their emission probabilities

In the second part of my presentation, I will discuss the measurement of high frequency noise [4] generated by the random transfer of fractional excitations through a potential barrier biased with a dc voltage Vdc. At high frequencies (few GHz), the emitted noise can be interpreted as the generation of microwave photons in a coaxial measurement line weakly coupled to the sample. We observe that photons are only emitted when their frequency is smaller than the frequency threshold fJ=qVdc/h called the Josephson frequency [5,6] in analogy with the Josephson relation in superconductors. This threshold provides a direct determination of the fractional charge q.

[1] E. Bocquillon et al. Science 339, 1054 (2013)
[2] C. Grenier et al. NJP 13, 093007 (2011)
[3] T. Jullien et al. Nature 514, 603 (2014)
[4] R. Bisognin et al., Nature Communications 10, 1708 (2019).
[5] C. de C. Chamon, D. E. Freed, and X. G. Wen, Phys. Rev. B, 51, 2363 (1995).
[6] M. Kapfer et al., Science 363, 846 (2019).