Defoort, M. and Dufresnes, S. and Ahlstrom, S. L. and Bradley, D. I. and Haley, R. P. and Guénault, A. M. and Guise, E. A. and Pickett, G. R. and Poole, M. and Woods, A. J. and Tsepelin, V. and Fisher, S. N. and Godfrin, H. and Collin, E. (2016) Probing Bogoliubov Quasiparticles in Superfluid $$^3$$ 3 He with a ‘Vibrating-Wire Like’ MEMS Device. Journal of Low Temperature Physics, 183 (3). pp. 284-291. ISSN 0022-2291
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Abstract
We have measured the interaction between superfluid 3He–B and a micro-machined goalpost-shaped device at temperatures below 0.2Tc. The measured damping follows well the theory developed for vibrating wires, in which the Andreev reflection of quasiparticles in the flow field around the moving structure leads to a nonlinear frictional force. At low velocities, the damping force is proportional to velocity, while it tends to saturate for larger excitations. Above a velocity of 2.6 mm s−1, the damping abruptly increases, which is interpreted in terms of Cooper-pair breaking. Interestingly, this critical velocity is significantly lower than that reported with other mechanical probes immersed in superfluid 3He. Furthermore, we report on a nonlinear resonance shape for large motion amplitudes that we interpret as an inertial effect due to quasiparticle friction, but other mechanisms could possibly be invoked as well.