Characterization and control of charge transfer in a tunnel junction

Abstract

AbstractCharge transfer in a tunnel junction is studied under dc and ac voltage bias using quantum shot noise. Under dc voltage bias V, spectral density of noise measured within a very large bandwidth enables to deduce the current–current correlator in the time domain by Fourier transform. This correlator exhibits regular oscillations proving that electrons try to cross the junction regularly, every . Using harmonic and bi‐harmonic ac voltage bias, we then show that quasiparticles excitations can be transferred through the junction in a controlled way. By measuring the reduction of the excess shot noise, we are able to determine the number of electron–hole pairs surrounding the injected electrons and demonstrate that bi‐harmonic voltage pulses realize an on‐demand electron source with a very small admixture of electron–hole pairs.A time‐dependent voltage drive applied to a contact with transmission generates an incoming excitation giving rise to transmitted and reflected quasiparticles. The excess noise given by the difference between the noise measured with and without the ac excitation is measured by an ammeter with a bandwidth . It gives the number of electron–hole pairs surrounding the transmitted electrons: where is the repetition frequency of .