Transient charge and energy flow in the wide-band limit

TL;DR

This paper examines the wide-band limit approximation in nanoscale transport, revealing its limitations in short-time dynamics and proposing solutions for accurate modeling of charge and energy flow under biases and temperature gradients.

Contribution

It identifies the failure of the wide-band limit to capture short-time behaviors in molecular junctions and offers explanations and solutions for this issue.

Findings

Charge current shows a discontinuity with temperature gradients.

Energy flow diverges when voltage bias is applied with temperature gradients.

The approximation accurately describes long-time transport but not short-time dynamics.

Abstract

The wide-band limit is a commonly used approximation to analyze transport through nanoscale devices. In this work we investigate its applicability to the study of charge and heat transport through molecular break junctions exposed to voltage biases and temperature gradients. We find that while this approximation faithfully describes the long-time charge and heat transport, it fails to characterize the short-time behavior of the junction. In particular, we find that the charge current flowing through the device shows a discontinuity when a temperature gradient is applied, while the energy flow is discontinuous when a voltage bias is switched on and even diverges when the junction is exposed to both a temperature gradient and a voltage bias. We provide an explanation for this pathological behavior and propose two possible solutions to this problem.