We investigate the electromechanical properties of quartz bulk acoustic wave resonators at extreme cryogenic temperatures. By applying a DC bias voltage, we demonstrate broad frequency tuning of high-Q phonon modes in a quartz bulk acoustic wave cavity at cryogenic temperatures of 4 K and 20 mK. More than 100 line-widths of tuning of the resonance peak without any degradation in loaded quality factor, which are as high as 1.73×109, is seen for high order overtone modes. For all modes and temperatures the observed coefficient of frequency tuning is ≈ 3.5 mHz/V per overtone number n corresponding to a maximum of 255.5 mHz/V for the n=73 overtone mode. No degradation in the quality factor is observed for any value of applied biasing field.
@article{arxiv.2207.01176,
title = {Electro-Mechanical Tuning of High-Q Bulk Acoustic Phonon Modes at Cryogenic Temperatures},
author = {William M. Campbell and Serge Galliou and Michael E. Tobar and Maxim Goryachev},
journal= {arXiv preprint arXiv:2207.01176},
year = {2025}
}