Electrical clamping losses in a piezoelectric mechanical resonator

LTL Quantum Physics Seminar (Nanotalo). Speaker: Mr. Alpo Välimaa (Aalto University, Finland).

High quality factors of mechanical resonators are essential for several applications of electromechanical devises. In particular, this holds true for studies near the quantum limit of mechanical vibrations. Energy leakage through supports is a series limiting factor for high quality factors. Various approaches have been realized to mitigate this problem, for example, design of anchor points, or inclusion of phononic shields. Here we investigate how the quality factors of mm-sized quartz resonators are limited by clamping losses at deep cryogenic temperatures. We first introduce means to improve the mechanical quality factor (Q) by up to two orders of magnitude in a no-clamping scheme. We can exclude a wide coverage of aluminum metallization on the disk or bond wires as sources of dissipation. However, we find dramatic reduction of Q-factor accompanying a special metallization pattern that involves strong focusing of the vibrations in the disk center. In the on-going work, we propose that the Q-factor is reduced because mechanical energy leaks electrically out through electrical clamping points. This presents a new mechanism for clamping losses of mechanical resonator, and highlights the importance of rigid electrical boundary conditions.