The dark side of DFT based transport calculations

Area of Science:

• Condensed Matter Physics
• Quantum Chemistry
• Materials Science

Background:

• Density Functional Theory (DFT) is a common method for electronic structure calculations.
• Accurately calculating electron transport properties, like conductance, is crucial for device applications.
• Previous studies have primarily focused on non-interacting or weakly interacting systems.

Purpose of the Study:

• To compare the conductance of a realistic interacting electron system with its Kohn-Sham counterpart within DFT.
• To investigate the limitations of standard DFT in predicting conductance for strongly correlated systems.
• To propose a potential solution for improving DFT's accuracy in transport calculations.

Main Methods:

• Calculated the conductance of a six-site interacting ring system threaded by magnetic flux π.
• Computed the conductance of the corresponding Kohn-Sham particles using lattice DFT.
• Employed symmetry analysis to understand the behavior of the conductance.

Main Results:

• The conductance of Kohn-Sham particles was found to be exactly zero due to symmetry.
• The conductance of the physical interacting system was close to the unitary limit.
• Demonstrated that linear conductance is not accurately given by Kohn-Sham particle conductance.

Conclusions:

• Standard DFT, even with exact functionals, fails to capture the conductance of interacting systems accurately.
• A fundamental disconnect exists between Kohn-Sham particle behavior and physical system conductance.
• Extending the standard DFT framework is essential for reliable electronic transport predictions in correlated materials.