Breaking the simple proportionality between molecular conductances and charge transfer rates

Area of Science:

• Theoretical chemistry
• Molecular electronics
• Condensed matter physics

Background:

• Understanding charge transport in molecular systems is crucial for developing molecular electronic devices.
• The relationship between molecular conductance and charge transfer rates is complex and not fully understood.
• Existing models often struggle to account for environmental effects like decoherence.

Purpose of the Study:

• To develop a unified theoretical framework for describing charge transfer across molecular bridges.
• To elucidate the relationship between molecular conductance and charge transfer rates as a function of molecular properties and environmental factors.
• To explain observed correlations between molecular conductance and electrochemical kinetics.

Main Methods:

• Utilized a reduced density matrix formulation to model charge transfer kinetics, incorporating system-bath couplings.
• Employed a Green's function based Landauer-Buttiker method to calculate steady-state currents.
• Developed a framework applicable across different transport regimes, including bath-induced decoherence effects.

Main Results:

• Established a power-law relationship between molecular conductances and charge transfer rates.
• Demonstrated that nonlinear rate-conductance relationships arise from variations in charge transport barrier heights.
• Showed that environmental decoherence rates also contribute to the nonlinear rate-conductance behavior.

Conclusions:

• The presented theoretical framework successfully describes the interplay between molecular conductance and charge transfer rates.
• The model provides a unified explanation for previously puzzling correlations in molecular systems.
• This work offers insights into designing molecular components with tailored electronic and kinetic properties.