Characterization and control of charge transfer in a tunnel junction

TL;DR

This paper investigates charge transfer in a tunnel junction under dc and ac biases using quantum shot noise, revealing electron crossing regularity and demonstrating controlled quasiparticle transfer with minimal electron-hole pairs.

Contribution

It introduces a method to analyze charge transfer via shot noise and demonstrates controlled quasiparticle injection using bi-harmonic voltage pulses.

Findings

Electrons cross the junction regularly every h/eV.

Bi-harmonic voltage pulses enable on-demand electron sources.

Reduction of shot noise quantifies electron-hole pair admixture.

Abstract

Charge 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 $h/eV$. 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.