Quantum Friction of Micromechanical Resonators at Low Temperatures

TL;DR

This paper investigates quantum-mechanical dissipation mechanisms in micromechanical resonators at low temperatures, revealing a phonon pumping process and superradiance effects that influence internal friction.

Contribution

It introduces a novel phonon pumping mechanism and superradiance effects as key factors in quantum friction of micromechanical resonators, expanding understanding of dissipation at quantum scales.

Findings

Weakly temperature-dependent internal friction observed.

Superradiance enhances dissipation in small structures.

Phonon pumping causes novel quantum friction effects.

Abstract

Dissipation of micro- and nano-scale mechanical structures is dominated by quantum-mechanical tunneling of two-level defects intrinsically present in the system. We find that at high frequencies--usually, for smaller, micron-scale structures--a novel mechanism of phonon pumping of two-level defects gives rise to weakly temperature-dependent internal friction, $Q^{-1}$, concomitant to the effects observed in recent experiments. Due to their size, comparable to or shorter than the emitted phonon wavelength, these structures suffer from superradiance-enhanced dissipation by the collective relaxation of a large number of two-level defects contained within the wavelength.