Time-Dependent Transport Through Molecular Junctions

TL;DR

This paper explores the time-dependent electronic transport in molecular junctions under pulsed and AC biases, revealing how lead structure, bias frequency, and junction properties influence current response and phase lag.

Contribution

It introduces a combined approach using Green functions and ab initio calculations to analyze dynamic transport in molecular junctions, highlighting frequency-dependent behaviors.

Findings

Short time response varies with lead structure and bias.

Low frequency AC bias causes current to track or lead the bias.

High frequency bias results in current lag due to kinetic inductance.

Abstract

We investigate transport properties of molecular junctions under two types of bias--a short time pulse or an AC bias--by combining a solution for the Green functions in the time domain with electronic structure information coming from ab initio density functional calculations. We find that the short time response depends on lead structure, bias voltage, and barrier heights both at the molecule-lead contacts and within molecules. Under a low frequency AC bias, the electron flow either tracks or leads the bias signal (capacitive or resistive response) depending on whether the junction is perfectly conducting or not. For high frequency, the current lags the bias signal due to the kinetic inductance. The transition frequency is an intrinsic property of the junctions.