Topic
Liquid helium
About: Liquid helium is a research topic. Over the lifetime, 7218 publications have been published within this topic receiving 83977 citations.
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29 Mar 1991
TL;DR: In this paper, the structure of quantized vortices is described and a nucleation procedure for quantized V2V arrays is proposed, which is based on quantum turbulence and mutual friction.
Abstract: Preface 1. Background on classical vortices 2. Background on liquid helium II 3. Vortex dynamics and mutual friction 4. The structure of quantized vortices 5. Vortex arrays 6. Vortex waves 7. Quantum turbulence 8. Nucleation of quantized vortices Index.
1,393 citations
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TL;DR: In this paper, the first principles for the first-principle calculation of the rate of decay of a metastable phase were outlined for a wide variety of thermally activated nucleation and growth processes, possibly including decay of superflow in liquid helium.
1,008 citations
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TL;DR: In this article, it was argued that the wave function representing an excitation in liquid helium should be nearly of the form Σif(ri)φ, where φ is the ground-state wave function, f(r) is some function of position, and the sum is taken over each atom i.i.
Abstract: It is argued that the wave function representing an excitation in liquid helium should be nearly of the form Σif(ri)φ, where φ is the ground-state wave function, f(r) is some function of position, and the sum is taken over each atom i. In the variational principle this trial function minimizes the energy if f(r)=exp(ik·r), the energy value being E(k)=2k2/2mS(k), where S(k) is the structure factor of the liquid for neutron scattering. For small k, E rises linearly (phonons). For larger k, S(k) has a maximum which makes a ring in the diffraction pattern and a minimum in the E(k) vs k curve. Near the minimum, E(k) behaves as Δ+2(k-k0)2/2μ, which form Landau found agrees with the data on specific heat. The theoretical value of Δ is twice too high, however, indicating need of a better trial function.
Excitations near the minimum are shown to behave in all essential ways like the rotons postulated by Landau. The thermodynamic and hydrodynamic equations of the two-fluid model are discussed from this view. The view is not adequate to deal with the details of the λ transition and with problems of critical flow velocity.
In a dilute solution of He3 atoms in He4, the He3 should move essentially as free particles but of higher effective mass. This mass is calculated, in an appendix, to be about six atomic mass units.
665 citations
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TL;DR: In this paper, the authors showed that there is a drop in viscosity below the λ-point by a factor of 3 compared with liquid helium at normal pressure, and a difference of 8 compared with the value just above the point of interest.
Abstract: THE abnormally high heat conductivity of helium II below the λ-point, as first observed by Keesom, suggested to me the possibility of an explanation in terms of convection currents. This explanation would require helium II to have an abnormally low viscosity; at present, the only viscosity measurements on liquid helium have been made in Toronto1, and showed that there is a drop in viscosity below the λ-point by a factor of 3 compared with liquid helium at normal pressure, and by a factor of 8 compared with the value just above the λ-point. In these experiments, however, no check was made to ensure that the motion was laminar, and not turbulent.
659 citations
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TL;DR: In this article, the Bragg-Williams-Betheoretic transition between n holes and n helium atoms in a body-centred cubic lattice of 2n places is treated as a phase transition of second order in close analogy to the transition observed with I-brass.
Abstract: IN a recent paper1 Frohlich has tried to interpret the λ-phenomenon of liquid helium as an order–disorder transition between n holes and n helium atoms in a body-centred cubic lattice of 2n places. He remarks that a body-centred cubic lattice may be considered as consisting of two shifted diamond lattices, and he assumes that below the λ-point the helium atoms prefer the places of one of the two diamond lattices. The transition is treated on the lines of the Bragg-Williams-Bethe theory as a phase transition of second order in close analogy to the transition observed with I-brass. Jones and Allen in a recent communication to NATURE2 also referred to this idea. In both these papers, use is made of the fact, established by the present author, that with the absorbed abnormally great molecular volume of liquid helium (caused by the zero motion3) the diamond-configuration has the lowest potential energy among all regular lattice structures4.
610 citations