Influence of long-range interactions on quantum interference in molecular conduction. A tight-binding (Hückel)...

Area of Science:

• Quantum Chemistry
• Molecular Electronics
• Condensed Matter Physics

Background:

• Quantum interference (QI) significantly suppresses electron transmission in π-conjugated molecules connected to electrodes.
• Standard Hückel molecular orbital (HMO) models show deviations from experimental and advanced computational results for QI phenomena.

Purpose of the Study:

• To extend the HMO method by incorporating non-nearest-neighbor interactions (long-range interactions, LRIs).
• To develop a geometric modification within the HMO model to account for bond rotations.
• To improve the accuracy of predicting quantum interference effects in molecular systems.

Main Methods:

• Implemented LRIs in the HMO model using a damping function based on topological distance.
• Incorporated geometric modifications, specifically rotation around single bonds, into the extended HMO model.
• Validated results against Density Functional based Tight-Binding (DFTB) calculations and experimental data.

Main Results:

• LRIs were found to alter the position and intensity of QI-induced antiresonance peaks, sometimes suppressing QI.
• The geometric LRI model accurately reproduced transmission changes due to bond rotation in biphenyl.
• Results align well with DFTB calculations and experimental observations for molecular systems.

Conclusions:

• The extended HMO model with LRIs and geometric modifications provides a more accurate description of quantum interference phenomena.
• This approach offers a valuable tool for understanding and predicting electron transport in molecular junctions.
• The findings enhance molecular orbital theory and graph-theoretic path-counting models for electron transport studies.