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Jeudi 7 mai
Non-equilibrium current fluctuations provide invaluable supplementary information to the regular conductivity measurements in nanoscale samples. We have studied this noise, called as 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 as a function 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. In my presentation, I will introduce the main results of our investigations with superconducting contacts and discuss briefly our preliminary experiments on the current-phase relation in graphene Josephson junctions.