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Probing superfluid He4 with high-frequency nanomechanical resonators down to millikelvin temperatures

“…(a) (Color Online) Magnetic field dependence of damping for 150 µm and 30 µm-long beams operated in vacuum and superfluid 4 He at 10 mK. Damping at high magnetic fields follows B 2 dependence (shown with dashed lines) as a result of magnetomotive loading in nanobeams21 . Towards low magnetic fields Q −1 tot becomes constant as we approach the internal damping of the beams in vacuum along with acoustic emission in the liquid.…”

Detecting a phonon flux in superfluid He4 by a nanomechanical resonator

“…As the magnetic field is increased beyond ≈ 50 mT, the aluminum film becomes normal and the increase of internal damping decreases the quality factor to ∼ 10 6 . This damping is independent of the magnetic field up to 150 mT, above which the dissipation arising from moving the conductor in the magnetic field (magnetomotive loading) starts to dominate, with the expected B 2 dependence [15].…”

Tunneling Systems in Amorphous and Crystalline Solids

“…Furthermore, an additional damping mechanism is related to the oscillation of metallic samples in a magnetic field that causes eddy currents with an energy dissipation proportional to the square of the applied magnetic field (Voncken et al (1997)). The cooling of a sample to the lowest temperatures depends on whether the thermal conductivity of the sample is governed by phonons only as it is the case in dielectrics or in metals in the superconducting state far below the superconducting transition temperature, or whether electrons play the most important role in the heat transfer within the sample.…”