Charge fluctuations and feedback effect in shot noise in a Y-terminal system

TL;DR

This paper studies charge fluctuations and feedback effects in shot noise within a three-terminal quantum system, revealing how Coulomb interactions and multiple levels influence current correlations and noise characteristics.

Contribution

It introduces a spectral decomposition method to analyze charge fluctuation effects on shot noise and correlations in multi-level and double quantum dot Y-terminal systems.

Findings

Charge fluctuations at the lowest tunneling rate level cause super-Poissonian noise.

At higher voltages, electrons transfer independently with multiple levels involved.

Feedback effects in double quantum dots enhance shot noise through Coulomb blockade.

Abstract

We investigate a dynamical Coulomb blockade effect and its role in the enhancement of current-current correlations in a three-terminal device with a multilevel splitter, as well as with two quantum dots. Spectral decomposition analysis shows that in the Y-terminal system with a two level ideal splitter, charge fluctuations at a level with a lowest outgoing tunneling rate are responsible for a super-Poissonian shot noise and positive cross-correlations. Interestingly, for larger source-drain voltages, electrons are transferred as independent particles, when three levels participate in transport, and double occupancy is allowed. We can explain compensation of the current correlations as the interplay between different bunching and antibunching processes by performing a spectral decomposition of the correlation functions for partial currents flowing through various levels. In the system with two quantum dots acting as a splitter, a long range feedback effect of fluctuating potentials leads to the dynamical Coulomb blockade and an enhancement of shot noise.