Surface Waves on Superfluid 4He Under Reduced Gravity

Abstract

Superfluid 4 He was produced on a small jet plane for the first time using a small GM-refrigerator to condense the liquid and a scroll pump to get the superfluid by evaporation. The surface wave on superfluid under 0.5g E , 0.1g E and 0.05g E , together with 2g E and 1g E , was successfully examined by an optical method utilizing parabolic flight. Here, g E is the gravitational constant on the ground. Assuming that only the fundamental mode was excited as determined by the sample cell width, the resonance peak in the frequency domain was well reproduced by the gravity wave with corresponding gravity constant.

Ripening of splashed4He crystals by acoustic waves with and without gravity

“…To prevent liquid 3 He from overflowing into the pumping tube, steel wool was placed into the 3 He pot, which sucked out the 3 He liquid during the zero-gravity periods due to the large surface area. The 3 He pot was pumped by a scroll pump and exhausted in approximately 7 h, with the lowest temperature of 0.60 K. Details of the cryostat and operation procedures can be found in our previous publications [16][17][18].…”

Gravity waves on the surface of topological superfluid 3He-B

“…For such observation it is not enough to cool 3 He below its critical temperature T c ≈ 10 −3 K. At temperatures close to T c viscosity of the normal component of 3 He is high, oil-like, and the surface waves are overdamped [1]. Only the third sound waves in a thin film, where the normal component is clamped, have been previously observed in 3 He-B at (0.3 ÷ 0.8) T c [10].…”

“…Waves on the surface of a fluid in a gravitational field [1] present a universal phenomenon in a wide range of systems, from a glass of drink to hot astrophysical objects [2] and cold superfluids [3]. Properties of the waves provide an important information about the fluid itself which in turn can result in useful practical applications.…”

“…Recently the surface properties of the fermionic 3 He in its superfluid B phase have attracted a lot of attention owing to non-trivial topology of this superfluid: It is expected that fermionic bound states with Majorana character emerge at the surface [5][6][7][8]. While in solidstate systems complex engineering efforts are required to obtain Majorana fermions [9], the free surface of 3 He-B should be naturally covered by a thin layer of such states. Could this 'film' in a sense 'still' the surface waves of 3 He-B and is it possible to observe this damping in the experiment?…”

“…While in solidstate systems complex engineering efforts are required to obtain Majorana fermions [9], the free surface of 3 He-B should be naturally covered by a thin layer of such states. Could this 'film' in a sense 'still' the surface waves of 3 He-B and is it possible to observe this damping in the experiment? While this question awaits a proper theoretical consideration we report here the first, to our knowledge, observation of gravity waves on the surface of 3 He-B.…”