Calculation of the current response in a nanojunction for an arbitrary time-dependent bias: application to the molecular wire

TL;DR

This paper develops an efficient numerical method to calculate time-dependent electron current in molecular junctions under arbitrary biases, using the Wide Band Limit Approximation and Padé expansion, with applications to molecular wires.

Contribution

It introduces a novel numerical scheme that simplifies current calculations by removing frequency integrals analytically and handles sinusoidal biases efficiently.

Findings

The method accurately computes current and particle number in molecular wires.

Finite size effects influence the current response after bias switch-on.

The approach is applicable to arbitrary time-dependent biases in quantum transport.

Abstract

Recently [Phys. Rev. B 91, 125433 (2015)] we derived a general formula for the time-dependent quantum electron current through a molecular junction subject to an arbitrary time-dependent bias within the Wide Band Limit Approximation (WBLA) and assuming a single particle Hamiltonian. Here we present an efficient numerical scheme for calculating the current and particle number. Using the Pad\'e expansion of the Fermi function, it is shown that all frequency integrals occurring in the general formula for the current can be removed analytically. Furthermore, when the bias in the reservoirs is assumed to be sinusoidal it is possible to manipulate the general formula into a form containing only summations over special functions. To illustrate the method, we consider electron transport through a one-dimensional molecular wire coupled to two leads subject to out-of-phase biases. We also investigate finite size effects in the current response and particle number that results from the switch-on of such a bias.