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Molecular transport junctions: asymmetry in inelastic tunneling processes
Michael Galperin1, Abraham Nitzan, Mark A Ratner
1Department of Chemistry and Materials Research Center, Northwestern University, Evanston, Illinois 60208, USA. misha@chem.northwestern. edu
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Asymmetry in inelastic electron tunneling spectroscopy (IETS) arises from differing energy dependencies of contact self-energies. This finding explains observed asymmetries in IETS measurements, offering new insights into electronic transport.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Inelastic electron tunneling spectroscopy (IETS) typically analyzes symmetric conduction/voltage characteristics in the Ohmic regime.
- Inelastic features in IETS, observed via d(2)I/dV(2), are often symmetric but can exhibit asymmetry.
Purpose of the Study:
- To investigate the origins of asymmetry in IETS measurements.
- To theoretically explain the observed asymmetry in inelastic features.
Main Methods:
- Utilizing a nonequilibrium Green function approach.
- Analyzing the energy dependence of contact self-energies and their impact on IETS.
Main Results:
- Asymmetry in IETS is attributed to differing energy dependencies of the two contact self-energies.
- This asymmetry is linked to variations in contact density of states or coupling energy dependence.
- The degree of asymmetry scales with the difference in energy-dependent self-energies.
Conclusions:
- The study provides a theoretical framework for understanding asymmetry in IETS.
- This understanding can be applied to analyze complex electronic transport phenomena in molecular junctions.
- The nonequilibrium Green function method offers advantages over WKB scattering theory for these analyses.
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