Dissipation due to tunneling two-level systems in gold nanomechanical resonators

TL;DR

This study investigates how two-level systems in gold nanomechanical resonators cause energy loss and frequency shifts at very low temperatures, revealing temperature-dependent dissipation behaviors similar to amorphous solids.

Contribution

First measurement of dissipation and frequency shift in gold nanomechanical resonators at millikelvin temperatures highlighting two-level systems as the dominant dissipation mechanism.

Findings

Dissipation increases as T^{0.5} from 30 mK to 500 mK.

Frequency shift shows a logarithmic temperature dependence.

Dissipation saturates at higher temperatures.

Abstract

We present measurements of the dissipation and frequency shift in nanomechanical gold resonators at temperatures down to 10 mK. The resonators were fabricated as doubly-clamped beams above a GaAs substrate and actuated magnetomotively. Measurements on beams with frequencies 7.95 MHz and 3.87 MHz revealed that from 30 mK to 500 mK the dissipation increases with temperature as $T^{0.5}$, with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behavior of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems.