The dark side of DFT based transport calculations

TL;DR

This paper reveals a fundamental limitation of standard DFT in transport calculations, showing that Kohn-Sham particles can have zero conductance while the physical system is highly conductive, and proposes extensions to address this issue.

Contribution

The paper demonstrates a fundamental flaw in lattice DFT for transport and suggests possible extensions to overcome this limitation.

Findings

Kohn-Sham conductance is exactly zero in the studied system.

Physical conductance is close to the unitary limit.

Standard DFT scheme may require extension to accurately predict conductance.

Abstract

We compare the conductance of an interacting ring of six lattice sites threaded by flux $\pi$ in a two terminal setup with the conductance of the corresponding Kohn-Sham particles. Based on symmetry considerations we can show that even within (lattice) Density Functional Theory employing the exact Functional the conductance of the Kohn-Sham particles is exactly zero, while the conductance of the physical system is close to the unitary limit. We show that this fundamental problem might be solved by extending the standard DFT scheme.