Co-tunneling current and shot noise in quantum dots

TL;DR

This paper develops a comprehensive theoretical framework for calculating current and shot noise in quantum dots, incorporating non-Markovian effects and co-tunneling processes, applicable to complex systems like molecules.

Contribution

It introduces a general, second-order diagrammatic approach that accounts for co-tunneling and non-Markovian effects in quantum dot transport, extending previous models.

Findings

Super-Poissonian shot noise observed due to spin-flip co-tunneling.

Noise characteristics depend sensitively on coupling strength.

Theory applicable to a broad range of quantum systems.

Abstract

We derive general expressions for the current and shot noise, taking into account non-Markovian memory effects. In generalization of previous approaches our theory is valid for arbitrary Coulomb interaction and coupling strength and is applicable to quantum dots and more complex systems like molecules. A diagrammatic expansion up to second-order in the coupling strength, taking into account co-tunneling processes, allows for a study of transport in a regime relevant to many experiments. As an example, we consider a single-level quantum dot, focusing on the Coulomb-blockade regime. We find super-Poissonian shot noise due to spin-flip co-tunneling processes at an energy scale different from the one expected from first-order calculations, with a sensitive dependence on the coupling strength.