Evidence for the role of normal-state electrons in nanoelectromechanical damping mechanisms at very low temperatures

TL;DR

This study demonstrates that normal-state electrons significantly contribute to damping in nanoelectromechanical resonators at low temperatures, with dissipation greatly reduced in the superconducting state, enhancing device quality factors.

Contribution

It provides experimental evidence linking normal electrons to damping mechanisms in nanoelectromechanical systems, highlighting the role of electronic states in dissipation.

Findings

Dissipation is much lower in the superconducting state.

Normal electrons contribute significantly to damping.

Quality factors improve at very low temperatures.

Abstract

We report on experiments performed at low temperatures on aluminum covered silicon nanoelectromechanical resonators. The substantial difference observed between the mechanical dissipation in the normal and superconducting states measured within the same device unambiguously demonstrates the importance of normal-state electrons in the damping mechanism. The dissipative component becomes vanishingly small at very low temperatures in the superconducting state, leading to exceptional values for the quality factor of such small silicon structures. A critical discussion is given within the framework of the standard tunneling model.