Anomalous Damping of a Microelectromechanical Oscillator in Superfluid 3He-B

The mechanical resonance properties of a microelectromechanical oscillator with a gap of 1.25 μm was studied in superfluid He3-B at various pressures. The oscillator was driven in the linear damping regime where the damping coefficient is independent of the oscillator velocity. The quality factor of the oscillator remains low (Q≈80) down to 0.1Tc, 4 orders of magnitude less than the intrinsic quality factor measured in vacuum at 4 K. In addition to the Boltzmann temperature dependent contribution to the damping, a damping proportional to temperature was found to dominate at low temperatures. We propose a multiple scattering mechanism of the surface Andreev bound states to be a possible cause for the anomalous damping.