Study Of Superfluid He-3 Films With A Micro-Electro-Mechanical Device

A micro-electro-mechanical system (MEMS) device with a 1.25 mu m gap between a movable plate and the substrate was immersed in superfluid He-3 and cooled below 500 mu K at 21.2 bar. Mechanical resonances of its shear motion were monitored on warming from the base temperature. Our preliminary results demonstrate increasing damping and decreasing resonance frequencies with temperature, consistent with a thermal damping model caused by thermal quasiparticles. The quality factor (Q) of the oscillator remains surprisingly low (Q approximate to 30) down to 0.2 T/T-c, about 4 orders of magnitude smaller than the value in vacuum at 4K. The average superfluid gap was determined to be significantly suppressed from the value in bulk at the corresponding pressure.