Vibrational Energy Dissipation in Noncontact Single-Molecule Junctions Governed by Local Geometry and Electronic...

Area of Science:

• Surface science
• Molecular dynamics
• Quantum chemistry

Background:

• Adsorbate vibrational dynamics are crucial in single-molecule junctions.
• Energy dissipation into substrate electrons and phonons impacts molecular behavior.
• This affects spectral lines, vibrational lifetimes, and molecular manipulation.

Purpose of the Study:

• To develop an approach for disentangling adsorbate vibrational dynamics in noncontact junctions.
• To investigate the interplay of electron-phonon and phonon-phonon coupling.
• To understand vibrational mode specificity in CO-functionalized Cu surfaces.

Main Methods:

• Density Functional Theory (DFT)
• Machine learning
• Nonadiabatic molecular dynamics
• Computational modeling of single-molecule junctions

Main Results:

• Revealed strong vibrational mode specificity governed by electron-phonon and phonon-phonon coupling.
• Electron-phonon relaxation rates varied by two orders of magnitude and depended on tip-substrate geometry.
• Observed a weak nonadditive effect where electron-phonon coupling enhances phonon-phonon coupling.

Conclusions:

• The findings agree with experimental results from infrared spectroscopy and helium scattering.
• The study provides a framework to inform and enhance spectroscopy and scanning probe experiments.
• Highlights the importance of considering coupled energy dissipation channels for accurate predictions.