Electrode effects on the observability of destructive quantum interference in single-molecule junctions

Area of Science:

• Molecular electronics
• Quantum interference phenomena
• First-principles calculations

Background:

• Destructive quantum interference (QI) significantly impacts molecular electronic conductance.
• Understanding junction components is vital for interpreting experimental electron transport data.

Purpose of the Study:

• To investigate the structure-function relationship of transport in pyrene molecular junctions.
• To determine how anchor groups and electrodes affect destructive QI.
• To differentiate QI effects from electrode-induced features.

Main Methods:

• Non-equilibrium Green's function (NEGF) calculations.
• Density functional theory (DFT) framework.
• Analysis of pyrene molecular junctions with varying anchor groups and electrodes.

Main Results:

• Fermi level alignment, controlled by anchor groups and electrodes, dictates QI observability.
• Graphene electrodes introduce low-bias features mimicking QI, stemming from topological edge properties.
• Distinction between molecular and electrode contributions to transmission spectra was achieved.

Conclusions:

• First-principles analysis provides crucial insights for interpreting experimental QI studies in molecular junctions.
• Simple Hückel models are insufficient for accurately describing complex transport phenomena.
• The study guides experimentalists in identifying and understanding QI effects.