Coherent Acoustic Phonons in Plasmonic Nanoparticles: Elastic Properties and Dissipation at Low Temperatures

TL;DR

This study investigates the temperature-dependent elastic and dissipative properties of plasmonic gold nanostructures at cryogenic temperatures, revealing key insights for optimizing nanoresonator performance.

Contribution

It introduces a model linking elastic modulus and dissipation in nanostructures, highlighting external dissipation's role over internal friction in quality factor enhancement.

Findings

Oscillation frequencies increase linearly with decreasing temperature.

A dissipation peak occurs around 150 K due to thermally activated processes.

External dissipation factors are more influential than internal friction for quality factors.

Abstract

We studied the frequency and quality factor of mechanical plasmonic nanoresonators as a function of temperature, ranging from ambient to 4 K. Our investigation focused on individual gold nanorods and nanodisks of various sizes. We observed that oscillation frequencies increase linearly as temperature decreases until saturation is reached at cryogenic temperatures. This behavior is explained by the temperature dependence of the elastic modulus, with a Debye temperature compatible with reported bulk values for gold. To describe the behavior of the quality factor, we developed a model considering the nanostructures as anelastic solids, identifying a dissipation peak around 150 K due to a thermally activated process, likely of the Niblett-Wilks mechanism type. Importantly, our findings suggest that external dissipation factors are more critical to improving quality factors than internal friction, which can be increased by modifying the nanoresonator's environment. Our results enable the design of structures with high vibration frequencies and quality factors by effectively controlling external losses.