Background charges and quantum effects in quantum dots transport spectroscopy

TL;DR

This paper presents an extended model of charge traps in quantum dots that explains various experimental features, including conductance lines and negative differential conductance, especially in silicon nanowire quantum dots.

Contribution

The authors introduce a comprehensive model of background charges affecting quantum dot transport, providing new insights and predictions for experimental observations.

Findings

Single background charge causes conductance lines within Coulomb diamonds.

The model explains negative differential conductance far from degeneracy.

It accounts for anomalous features in silicon nanowire quantum dots.

Abstract

We extend a simple model of a charge trap coupled to a single-electron box to energy ranges and parameters such that it gives new insights and predictions readily observable in many experimental systems. We show that a single background charge is enough to give lines of differential conductance in the stability diagram of the quantum dot, even within undistorted Coulomb diamonds. It also suppresses the current near degeneracy of the impurity charge, and yields negative differential lines far from this degeneracy. We compare this picture to two other accepted explanations for lines in diamonds, based respectively on the excitation spectrum of a quantum dot and on fluctuations of the density-of-states in the contacts. In order to discriminate between these models we emphasize the specific features related to environmental charge traps. Finally we show that our model accounts very well for all the anomalous features observed in silicon nanowire quantum dots.