Inelastic tunneling effects on noise properties of molecular junctions

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 1-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.

16 pages, 11 figures

References in corpus (9)

• The Kondo effect in C${}_{60}$ single-molecule transistors
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• Shot Noise of a Quantum Shuttle
• Current noise in a vibrating quantum dot array
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Cited by in corpus (8)

• Molecular Transport Junctions: Vibrational Effects
• Phonon-assisted current noise in molecular junctions
• Electron-phonon interaction and full counting statistics in molecular junctions
• Charge transfer statistics of a molecular quantum dot with a vibrational degree of freedom
• Nonequilibrium isolated molecule limit
• Laser-induced currents along molecular wire junctions
• 1/f Tunnel Current Noise through Si-bound Alkyl Monolayers
• Quantum transport in a resonant tunnel junction coupled to a nanomechanical oscillator