Simple and Accurate Method for Time-Dependent Transport along Nanoscale Junctions

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• 作者：Liping Chen ; Thorsten Hansen ; Ignacio Franco
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 28, 2014
• 年：2014
• 卷：118
• 期：34
• 页码：20009-20017
• 全文大小：387K
• ISSN：1932-7455

文摘

A simple method that accurately captures the dynamics of metal鈥搈olecule鈥搈etal junctions under the influence of time-dependent driving forces is presented. In the method, the metallic contacts are modeled explicitly as a discrete set of levels that are dynamically broadened via an artificial damping term in the equations of motion. The approximations that underlie the method are revealed via a derivation of the effective equations of motion within the framework of nonequilibrium Green鈥檚 functions (NEGF) theory. As shown, the method applies to junctions that can be described by an effective independent Fermion Hamiltonian, admits arbitrary time dependence in the molecular Hamiltonian, and is restricted to time-dependent voltages that are adiabatically slow. The method is trivial to implement computationally, has a well-defined range where the results are independent of artificial model parameters, and is numerically shown to quantitatively reproduce the time-dependent transport characteristics of a model molecular junction driven by laser fields as described by an exact NEGF method in the wide band limit. As such, it generalizes previous efforts to capture Landauer transport via effective Liouville equations of motion with damping terms and constitutes an intuitive and technically accessible method for modeling time-dependent transport phenomena in molecular junctions that are driven by electric fields or fluctuating environments.