Level occupation switching with density functional theory

TL;DR

This paper investigates charge transport in multi-orbital quantum dot systems using density functional theory, revealing how level occupation switching depends on energy differences and exchange-correlation functionals, with improved accuracy over existing functionals.

Contribution

It demonstrates the equivalence of a quantum dot setup to an effective single impurity Anderson model and introduces an improved exchange-correlation functional for better accuracy.

Findings

Existing functional captures qualitative behavior

Improved parametrization matches NRG results closely

Level occupation switching is highly sensitive to energy differences

Abstract

The charge transport properties of zero-temperature multi-orbital quantum dot systems with one dot coupled to leads and the other dots coupled only capacitatively are studied within density functional theory. It is shown that the setup is equivalent to an effective single impurity Anderson model. This allows to understand the level occupation switching effect as transitions between ground states of different integer occupations in the uncoupled dots. Level occupation switching is very sensitive to small energy differences and therefore also to the details of the parametrized exchange-correlation functionals. An existing functional already captures the effect on a qualitative level but we also provide an improved parametrization which is very accurate when compared to reference numerical renormalization group results.