Third Moment of Current Fluctuations in a Diffusive Conductor

There has been only a few attempts to push deeper the study of current fluctuations in mesoscopic conductors by tackling the measurement of higher order moments such as the third one <δI³>. Such measurements have been performed only in tunnel junctions and quantum dots, revealing physics hidden in the study of the second moment <δI²> such as the coupling with the environment or the ordering of operators in a quantum measurement. Even the statistics of current fluctuations in the simplest system, an electrical wire, has never been probed experimentally.
In this talk I will present the measurement of non-Gaussian current fluctuations in a coherent, diffusive conductor at low temperature. The data are obtained from the recording of voltage fluctuations across the conductor and a careful determination of environmental effects. We obtain a very good agreement between theory and experiment with no fitting parameters. By increasing the voltage we explore the cross-over from coherent to inelastic transport. We observe that the non-Gaussian character of current fluctuations is much more robust than predicted.