Surface Waves on the Superfluids \(^3\)He and \(^4\)He
Free surface waves were examined both in superfluids \(^3\)He and \(^4\)He with the premise that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work in \(^3\)He is one of the first of its kind, but in \(^4\)He, it was possible to produce a much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning \(T<\) 100 mK for \(^4\)He and \(T\sim \) 100 \(\upmu \)K for \(^3\)He. Dozens of surface wave resonances, including up to 11 overtones, were observed and monitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.
KeywordsSurface wave Superfluid Normal fluid Interdigital capacitor
We thank J.-P. Kaikkonen, A. J. Niskanen, A. Ya. Parshin, V. Peri, A. Salmela, A. Sebedash, and V. Tsepelin for valuable discussions and assistance. This work was supported in part by the European Union FP7/20072013, Grant No. 228464 Microkelvin and by the Academy of Finland, CoE 20122017, Grant No. 250280 LTQ. This research made use of the Aalto University Low Temperature Laboratory infrastructure. We also acknowledge the grants from Jenny and Antti Wihuri Foundation and the National Doctoral Programme in Materials Physics.