Time-dependent versus static quantum transport simulations beyond linear response

TL;DR

This study compares time-dependent and static quantum transport simulations beyond linear response, demonstrating that TDDFT reproduces steady-state currents accurately and confirming the equivalence of static and time-dependent approaches at low bias.

Contribution

It provides a rigorous comparison between TDDFT and DFT-NEGF for quantum transport, validating TDDFT's accuracy for steady-state currents beyond linear response.

Findings

TDDFT reproduces DFT-NEGF steady-state currents exactly.

Significant differences found with non-self-consistent treatments.

Static and time-dependent approaches are equivalent at low bias.

Abstract

To explore whether the density-functional theory non-equilibrium Green's function formalism (DFT-NEGF) provides a rigorous framework for quantum transport, we carried out time-dependent density functional theory (TDDFT) calculations of the transient current through two realistic molecular devices, a carbon chain and a benzenediol molecule inbetween two aluminum electrodes. The TDDFT simulations for the steady state current exactly reproduce the results of fully self-consistent DFT-NEGF calculations even beyond linear response. In contrast, sizable differences are found with respect to an equilibrium, non-self-consistent treatment which are related here to differences in the Kohn-Sham and fully interacting susceptibility of the device region. Moreover, earlier analytical conjectures on the equivalence of static and time-dependent approaches in the low bias regime are confirmed with high numerical precision.