Evidence of universality in the dynamical response of micromechanical diamond resonators at millikelvin temperatures

摘要

We report kelvin- to millikelvin-temperature measurements, of dissipation and frequency shift in megahertz-range resonators fabricated from ultrananocrystalline diamond. Frequency shift δf/f_0 and dissipation Q~(-1) demonstrate temperature dependence in the millikelvin range similar to that predicted by the glass model of tunneling two-level systems. The logarithmic temperature dependence of δf/f_0 is in good agreement with such models, which include phonon relaxation and phonon resonant absorplion. Dissipation shows a weak power law, Q~(-1)∝T~(1/3), followed by saturation at low temperature. A comparison of both the scaled frequency shift and dissipation in equivalent micromechanical structures made of single-crystal silicon and gallium arsenide indicates universality in the dynamical response.