Aluminum goalpost nano-mechanical devices at low temperatures

TL;DR

This paper characterizes metallic goalpost nano-mechanical structures at low temperatures, providing analytic models for their resonances, analyzing curvature effects, and discussing their applications in quantum fluids and friction studies.

Contribution

It extends existing literature by analytically modeling the resonances of goalpost nano-mechanical devices, including curvature and nonlinear effects, with good agreement to numerical simulations.

Findings

Analytic resonance models match numerical simulations.

Curvature and surface stress significantly affect device behavior.

Device motion and forces are expressed in SI units for quantum applications.

Abstract

Mechanical objects have been widely used at low temperatures for decades, for various applications; from quantum fluids sensing with vibrating wires or tuning forks, to torsional oscillators for the study of mechanical properties of glasses, and finally micro and nano-mechanical objects with the advent of clean room technologies. These small structures opened up new possibilities to experimentalists, thanks to their small size. We report on the characterization of purely metallic goalpost nano-mechanical structures, which are employed today for both quantum fluids studies (especially quantum turbulence in $^4$He, $^3$He) and intrinsic friction studies (Two-Level-Systems unraveling). Extending existing literature, we demonstrate the analytic modeling of the resonances, in good agreement with numerical simulations, for both first and second mechanical modes. Especially, the impact of the curvature of the whole structure (and therefore, in-built surface stress) is analyzed, together with nonlinear properties. We demonstrate that these are of geometrical origin, and device-dependent. Motion and forces are expressed in meters and Newtons experienced at the level of the goalpost's paddle, for any magnitude or curvature, which is of particular importance for quantum fluids and solids studies.