Higher harmonics and ac transport from time dependent density functional theory

TL;DR

This paper presents a method for simulating dynamical quantum transport in molecular devices using time-dependent density functional theory, revealing quantum effects on ac conductance and higher harmonics.

Contribution

It introduces an approximate TDFT-based approach with open boundary conditions for realistic molecular device simulations under ac bias.

Findings

Quantum effects influence ac conductance at small biases.

Dynamical simulations show fewer higher harmonics than classical models.

Current rectification behavior is briefly analyzed.

Abstract

We report on dynamical quantum transport simulations for realistic molecular devices based on an approximate formulation of time-dependent Density Functional Theory with open boundary conditions. The method allows for the computation of various properties of junctions that are driven by alternating bias voltages. Besides the ac conductance for hexene connected to gold leads via thiol anchoring groups, we also investigate higher harmonics in the current for a benzenedithiol device. Comparison to a classical quasi-static model reveals that quantum effects may become important already for small ac bias and that the full dynamical simulations exhibit a much lower number of higher harmonics. Current rectification is also briefly discussed.