Steady-State Density Functional Theory for Finite Bias Conductances

Area of Science:

• Condensed Matter Physics
• Quantum Chemistry
• Materials Science

Background:

• Electronic transport in nanoscale junctions is fundamental to molecular electronics.
• Density functional theory (DFT) is a powerful tool for studying electronic structure and properties.
• Describing steady-state transport, especially phenomena like Coulomb blockade, remains a challenge within DFT.

Purpose of the Study:

• To develop a novel DFT formalism for steady-state electronic transport.
• To establish a mapping between junction properties and basic variables (density, current).
• To investigate the role of exchange-correlation potentials in transport phenomena.

Main Methods:

• Formulation of a DFT-based transport theory using junction density and steady current as primary variables.
• Mathematical proof of a one-to-one mapping between variables and junction potential/bias near zero bias.
• Application to a model benzene junction.

Main Results:

• A Kohn-Sham system with two distinct exchange-correlation (xc) potentials is derived.
• Exchange-correlation potentials exhibit crucial steps in the density-current plane for weakly coupled junctions.
• The formalism successfully reproduces Coulomb blockade diamonds and aligns with orthodox theory for a benzene junction.

Conclusions:

• The proposed DFT formalism provides a robust framework for electronic transport in molecular junctions.
• The identified xc potential features are key to understanding Coulomb blockade.
• This work offers a new theoretical tool for designing and analyzing molecular electronic devices.