New approach to the observation of the condensate fraction in superfluid helium-4

Abstract

We present a phenomenological analysis of an experiment to observe the condensate fraction of helium-4 by firing low-energy pulses of helium atoms at suspended droplets of the superfluid and observing the resulting emission of helium atoms from the fluid. Emission occurs through a conventional process in which rotons are produced and propagate to the other side of the droplet, and through a second process depending on the existence of the condensate. If A is the area of the incoming beam, the cross section scales with A 2 (first process) and A 4 (second process), respectively, for small A. Aspects of a full many body calculation and the performance of such an experiment are briefly discussed.

Magnetic Levitation of liquid helium

“…A similar geometry of the liquid is required to perform proposed experiments on quantum tunneling of atoms through the superfluid condensate. 9 One way to avoid the troublesome forces of gravity is to perform experiments under free-fall conditions in space, where the residual accelerations ~~ are typically 10 -5 times the acceleration due to earth gravity. Before attempting this it is essential to perform preliminary experiments on the ground.…”

Quantum Sticking, Scattering, and Transmission ofH4eatoms from SuperfluidHCampbell1, Krotscheck2, Saarela3 1998Phys. Rev. Lett.Self Cite261120View full textAdd to dashboardCite

“…Experimental information is available about the scattering of helium atoms from helium surfaces and films [1][2][3][4][5]; from the dynamics of localized excitations within the fluid, including excitation scattering from the surface and quantum evaporation [5][6][7][8] ; and from inelastic neutron scattering at grazing angles from adsorbed films [9][10][11][12]. Moreover, information about the condensate fraction in helium may be obtainable directly from elastic transmission of 4 He atoms through superfluid 4 He slabs [13]. The fact that helium slabs have been made in the laboratory [14] leads to the prospect that the dynamic probes previously applied to adsorbed films and bulk surfaces of helium can now be applied to slabs.…”

High-quality variational wave functions for small4Heclusters

“…This work has been partially supported by grant PB97-1139 (Spain). 4 HeN droplets, using the interaction HFD-B(HE). VMC and DMC energies are taken from [11] for N ≤ 10, and [2] otherwise.…”

“…Variational Monte Carlo (VMC) calculations, using a Jastrow-like ansatz for the many-body wave function, are currently used for systems dominated by strong shortrange interactions. The VMC wave functions are the input for diffusion Monte Carlo (DMC), Green function Monte Carlo or path integral techniques which provide essentially exact, within statistical errors, ground state energies of 4 He clusters at zero temperature. Conversely, these calculations constitute a useful benchmark to test other many-body methods.…”