Fundamental and Environmental Contributions to the Cyclostationary Third Moment of Current Fluctuations in a Tunnel Junction

Current fluctuations generated by tunnel junctions are known to be non-Gaussian. However, this property is lost when fluctuations are measured at high frequency and limited bandwidth. We show that the quadratures of the electric field generated by a tunnel junction at frequency $f$ displays third order correlations, i.e. skewness, when the junction is electrically driven at $3f$, revealing the Poisonnian statistic of charge transfer by the barrier even at short time-scales. In addition to this intrinsic contribution from the junction, we observe extra correlations induced by the environmental noise at frequency $f$ as well as a feedback effects coming from the environmental impedance not only at frequency $f$ but also at some multiples of $f$.