title: Current and noise in a model of an alternating current scanning tunneling microscope molecule-metal junction.
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 photoassisted 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 photoassisted 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.
authors.affiliation: Centre de Physique Théorique, Case 907 Luminy, 13288 Marseille Cedex 9, France.
authors.forename: R
authors.initials: R
authors.lastname: Guyon
authors.forename: T
authors.initials: T
authors.lastname: Jonckheere
authors.forename: V
authors.initials: V
authors.lastname: Mujica
authors.forename: A
authors.initials: A
authors.lastname: Crépieux
authors.forename: T
authors.initials: T
authors.lastname: Martin