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» Conférences d’après mars 2011 : nouveau site

2373

Séminaire général du Département de physique

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Shot noise in graphene sheets and in graphene Josephson junctions
Pertti J. Hakonen (Helsinki)

7 mai 2009

Non-equilibrium current fluctuations provide invaluable supplementary information to the regular conductivity measurements in nanoscale samples. We have studied this noise, called shot noise, in graphene strips at cryogenic temperatures down to 50 mK. We find that the Fano factor (F = S_I /2e < I >) varies as a function of the carrier density and of the width-to-length ratio. At the Dirac point, the measured F is close to the universal value of 1/3 that is theoretically predicted for ideal, “pseudo-diffusive” graphene samples with W/L > 3. In my talk, I will present our experimental findings and discuss their implications on the nature of electrical transport in graphene. Using superconducting metal contacts, gate-controlled supercurrents can be generated in graphene. These Josephson junctions display clear signatures of multiple Andreev reflections, which leave pronounced fingerprints into the shot noise as well as into electrical conductivity. I will introduce the main results of our investigations with superconducting contacts and briefly discuss our preliminary experiments on the current-phase relation in graphene Josephson junctions.

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Non disponible Pertti J. Hakonen (Helsinki)
Pertti J. Hakonen belongs to the Helsinki University of Technology at Espoo (Finland).

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