Mutual interactions between objects oscillating in isotopically pure superfluid 4He in the T → 0 limit

Анотація

We report the results of experiments to explore interactions between physically separated oscillating objects in isotopically pure superfluid ⁴He at T ~ 10 mK. The investigations focused mainly on 32 kHz quartz tuning forks, but also consider a nearby 1 kHz oscillating grid. The low-drive linewidth (LDL) and resonant frequency f_d of a detector fork were monitored while the maximum velocity of a transmitter fork, separated from the detector by a few mm, was varied over a wide range. Clear evidence was found for mutual interactions between the two forks, and for the influence of the grid on the forks. Monitoring the detector's LDL and f_d provides evidence for a generator critical velocity in the range 0.3 < v_c1 <1.0 cm/s for onset of the detector responses, in addition to a second critical velocity v_c2 ~ 13 cm/s probably corresponding to the production of quantum turbulence at the generator. The results are discussed, but are not yet fully understood.