Inelastic tunneling effects on noise properties of molecular junctions

Michael Galperin, Abraham Nitzan, Mark A Ratner

Research output: Contribution to journalArticle

74 Citations (Scopus)

Abstract

The effect of electron-phonon coupling on the current noise in a molecular junction is investigated within a simple model. The model comprises a one-level bridge representing a molecular level that connects between two free electron reservoirs and is coupled to a vibrational degree of freedom representing a molecular vibrational mode. The latter in turn is coupled to a phonon bath that represents the thermal environment. We focus on the zero frequency noise spectrum and study the changes in its behavior under weak and strong electron-phonon interactions. In the weak coupling regime we find that the noise amplitude can increase or decrease as a result of opening of an inelastic channel, depending on distance from resonance and on junction asymmetry. In particular the relative Fano factor decreases with increasing off resonance distance and junction asymmetry. For resonant inelastic tunneling with strong electron-phonon coupling the differential noise spectrum can show phonon sidebands in addition to a central feature. Such sidebands can be observed when displaying the noise against the source-drain voltage, but not in noise vs gate voltage plots obtained at low source-drain bias. A striking crossover of the central feature from double to single peak is found for increasing asymmetry in the molecule-leads coupling or increasing electron-phonon interaction. These variations provide a potential diagnostic tool. A possible use of noise data from scanning tunneling microscopy experiments for estimating the magnitude of the electron-phonon interaction on the bridge is proposed.

Original languageEnglish
Article number075326
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume74
Issue number7
DOIs
Publication statusPublished - 2006

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Electron-phonon interactions
electron phonon interactions
Electrons
asymmetry
noise spectra
sidebands
Electric potential
Scanning tunneling microscopy
Lead
thermal environments
electric potential
Molecules
free electrons
scanning tunneling microscopy
baths
vibration mode
crossovers
electrons
estimating
degrees of freedom

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Inelastic tunneling effects on noise properties of molecular junctions. / Galperin, Michael; Nitzan, Abraham; Ratner, Mark A.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 74, No. 7, 075326, 2006.

Research output: Contribution to journalArticle

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