Assessing the importance of multireference correlation in predicting reversed conductance decay

Area of Science:

• Molecular electronics
• Quantum chemistry
• Condensed matter physics

Background:

• Classical resistors and most molecular systems exhibit conductance decay with increasing length (Ohm's Law).
• A phenomenon termed reversed conductance decay, where conductance increases with length, has been theoretically predicted but experimentally elusive.
• Discrepancies between theory and experiment are often attributed to theoretical multi-reference (static) correlation errors, which are challenging for standard methods.

Purpose of the Study:

• To experimentally investigate and confirm reversed conductance decay in molecular electronic systems.
• To quantify the precise role of static correlation in the phenomenon of reversed conductance decay.
• To compare the accuracy of multireference versus non-multireference theoretical methods in predicting this effect.

Main Methods:

• Development and application of a novel multireference transport method combining non-equilibrium Green's function (NEGF) and multiconfigurational pair-density functional theory (MCPDFT).
• Investigation of linear chains of phenyl rings with varying lengths and electrode configurations.
• Comparative analysis of NEGF-MCPDFT results against traditional non-multireference NEGF methods.

Main Results:

• Successful examination of a predicted case of reversed conductance decay in phenyl ring molecular chains.
• Quantification of the significant contribution of static correlation to reversed conductance decay.
• Demonstration of the limitations of non-multireference methods in accurately capturing this phenomenon.

Conclusions:

• The study provides experimental evidence for reversed conductance decay in molecular systems.
• Static correlation plays a crucial role in enabling reversed conductance decay, necessitating advanced theoretical treatments.
• The NEGF-MCPDFT method offers a more accurate approach for studying complex electronic transport phenomena in molecular devices.