Wetting of potassium surfaces by superfluid4He:A study using variational properties of the chemical potential

Abstract

The wetting of planar surfaces of K by superfluid 4 He films at Tϭ0 K is theoretically studied. In order to examine the consistency of numerical results, new variational properties of the chemical potential are derived. Two substrate-adsorbate interactions are analyzed: ͑a͒ the standard ''3-9'' one and ͑b͒ the more elaborated potential recently proposed by Chizmeshya, Cole, and Zaremba ͑CCZ͒. New results calculated within the framework of two different nonlocal density functionals ͑namely, those known as the Orsay-Paris and Orsay-Trento formalisms͒ are reported. It is demonstrated that the numerical solutions obtained from the theoretical equations verify with high accuracy the derived variational conditions. The main output of this investigation is the finding that, for both analyzed adsorption potentials, thick enough helium films exhibit a positive square of the third-sound velocity. The wetting of a potassium substrate by superfluid 4 He at T ϭ0 K suggested by experimental data is guaranteed in the case of the recent CCZ potential.

Structure and stability of superfluid4Hesystems with cylindrical symmetry

“…This regime is extended up to the critical value Ӎ0.088 Å 1/2 (n Ӎ130 Å Ϫ1 ), where ⍀/L becomes negative indicating that larger systems of 4 He are stable. 14,15 Note that this crossing of e and occurs just at the minimum of e in agreement with Eqs. ͑5.8͒ and ͑5.9͒.…”

“…On the other hand, hitherto no attention has been paid in the literature to 4 He adsorbed into weakly attractive cylindrical pores, which could be present in samples of alkali metals. Adsorption on planar surfaces of this kind of metals has already been extensively studied [10][11][12][13][14][15][16] leading to the important conclusion that the less attractive alkali, Cs, is not wet by 4 He at temperatures TՇ2 K. 17 All these facts have encouraged us to start an investigation of the behavior of 4 He adsorbed into nanopores in alkali metals.…”

From nonwetting to prewetting: The asymptotic behavior of4Hedrops on alkali substrates

“…11,14 For films of 4 He, and within the density-functional frame, 18 this criterion can be formulated in terms of the expansion coefficients of the total energy of the film in powers of 1/n. In particular, it has been shown that the OT density functional plus the CCZ potential yields, for 4 He films on alkali-metal substrates, wetting of Rb 18 and K, 31 and nonwetting of a Cs surface. 34 In Figs.…”

Adsorption of superfluid4Hefilms on planar heavy-alkali metals studied with the Orsay-Trento density functional

“…The main features of the adsorption on K and Cs could be interpreted in recent theoretical works. [10][11][12] In these studies, the calculations have been carried out by utilizing the improved NLDF formulation proposed by the Orsay-Trento ͑OT͒ Collaboration 13 and the more recent adsorption potential derived by Chizmeshya, Cole, and Zaremba 14 ͑CCZ potential͒. It should be noticed that for a given substrate the CCZ potential is more attractive than the old ͑9,3͒ interaction.…”