Optical response of metallic nanojunctions driven by single atom motion

TL;DR

This study uses ab initio calculations to reveal how atomic-scale reconfigurations in metallic nanojunctions cause abrupt changes in optical responses, linking transport quantization with plasmonic behavior at the atomic level.

Contribution

It demonstrates the direct connection between atomic reconfigurations, conductance quantization, and optical response in metallic nanojunctions, a novel insight into nanoscale optoelectronic behavior.

Findings

Atomic reorganization causes hysteresis in plasmonic response.

Jumps in optical spectra correspond to conductance quantization.

Atomic-scale dynamics influence optical properties significantly.

Abstract

The correlation between transport properties across sub-nanometric metallic gaps and the optical response of the system is a complex effect which is determined by the fine atomic-scale details of the junction structure. As experimental advances are progressively accessing transport and optical characterization of smaller nanojunctions, a clear connection between the structural, electronic and optical properties in these nanocavities is needed. Using ab initio calculations, we present here a study of the simultaneous evolution of the structure and the optical response of a plasmonic junction as the particles forming the cavity, two Na$_{380}$ clusters, approach and retract. Atomic reorganizations are responsible for a large hysteresis of the plasmonic response of the system, that shows a jump-to-contact instability during the approach process and the formation of an atom-sized neck across the junction during retraction. Our calculations demonstrate that, due to the quantization of the conductance in metal nanocontacts, atomic-scale reconfigurations play a crucial role in determining the optical response of the whole system. We observe abrupt changes in the intensities and spectral positions of the dominating plasmon resonances, and find a one-to-one correspondence between these jumps and those of the quantized transport as the neck cross-section diminishes. These results point out to an unforeseen connection between transport and optics at the atomic scale, which is at the frontier of current optoelectronics and can drive new options in optical engineering of signals driven by the motion and manipulation of single atoms.