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Current and noise in a model of an AC-STM molecule-metal junction

R. Guyon·T. Jonckheere·V. Mujica·A. Crepieux·T. Martin
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Abstract

The transport properties of a simple model for a finite level structure (a molecule or a dot) connected to metal electrodes in an alternating current scanning tunneling microscope (AC-STM) configuration is studied. The finite level structure is assumed to have strong binding properties with the metallic substrate, and the bias between the STM tip and the hybrid metal-molecule interface has both an AC and a DC component. The finite frequency current response and the zero frequency photo-assisted shot noise are computed using the Keldysh technique, and examples for a single site molecule (a quantum dot) and for a two-site molecule are examined. The model may be useful for the interpretation of recent experiments using an AC-STM for the study of both conducting and insulating surfaces, where the third harmonic component of the current is measured. The zero frequency photo-assisted shot noise serves as a useful diagnosis for analyzing the energy level structure of the molecule. The present work motivates the need for further analysis of current fluctuations in electronic molecular transport.

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R. Guyon, T. Jonckheere, V. Mujica, A. Crepieux, T. Martin. 2004-04-23. Current and noise in a model of an AC-STM molecule-metal junction. https://arxiv.org/abs/cond-mat/0404571

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