Transient dynamics of molecular devices under step-like pulse bias

TL;DR

This study uses first principles calculations to analyze the transient current response of molecular devices under step-like pulse bias, revealing the importance of resonant states and the need to go beyond the wideband limit for accurate modeling.

Contribution

It introduces a first principles approach to transient dynamics in molecular devices, emphasizing the role of resonant states and the limitations of the wideband approximation.

Findings

Longer time to reach steady state than transit time

Resonant states cause damped oscillations in current

Beyond wideband limit is necessary for accuracy

Abstract

We report first principles investigation of time-dependent current of molecular devices under a step-like pulse.Our results show that although the switch-on time of the molecular device is comparable to the transit time, much longer time is needed to reach the steady state. In reaching the steady state the current is dominated by resonant states below Fermi level. The contribution of each resonant state to the current shows the damped oscillatory behavior with frequency equal to the bias of the step-like pulse and decay rate determined by the life time of the corresponding resonant state. We found that all the resonant states below Fermi level have to be included for accurate results. This indicates that going beyond wideband limit is essential for a quantitative analysis of transient dynamics of molecular devices.