Properties of 3He in thin 4He films

Abstract

Substantial progress has been made in our understanding of the properties of 3He atoms in thin films of 4He. For such films the 3He occupies discrete quantum states in the film and the system is both rich and complex. Here we discuss progress in this field from several points of view; we briefly discuss early heat capacity and third sound results and concentrate on more recent NMR measurements of the magnetization and relaxation times T1 and T 2 . Further experimental work and theory for systems of finite 3He coverage is needed to fully understand this fascinating system.

4Heliquid-vapor interface below 1 K studied using x-ray reflectivity

“…Crossover from populating the lowest bound state to the second as 3 He coverage increases would lead to a step in heat capacity and affect NMR relaxation. Recent heat capacity measurements by Gasparini et al 17,18 and NMR by Hallock et al 19,20 are consistent with the existence of the second layer, but are not conclusive. Further measurements of this type may provide an estimate of the local surface density profile width.…”

“…[5][6][7][8][9][10][11][12][13][14] A number of physical phenomena of interest depend on the width of the interface between helium and its vapor. These include particle scattering off the surface of liquid helium, 15,16 and phenomena related to the existence of atomic, [17][18][19][20][21][22][23] and electron 24,25 bound states at the helium surface. The results we present can thus be compared with predictions based on either the theoretical estimates of the width, or on calculations based on experimental measurements of the surface excitation spectra.…”

Classical behaviour in the quantum liquid 3He–4He: Observation of a B2 dependence of the surface relaxation

“…A consequence is that the surface relaxation is independent of the He density. The finite solubility also explains the observation in He-He mixture films, that beyond a certain coverage of the surface with He, ¹ becomes nearly independent of the He coverage [23].…”

THE PROPERTIES OF THIN ^{3}He-^{4}He SUPERFLUID FILMS

“…The fact that the slope bends up in figure 3, that is, the third sound speed increases relative to what the third sound speed would be if all the 3 He were in the ground state, is an important constraint on models for third sound in this region. A second constraint, as will be discussed in section 4, comes from an analysis of the magnetization step data of [8,18,19].…”

“…In [12] a simple ideal quasi-particle picture is introduced to explain the magnetization steps of [8,18,19]. We apply a uniform magnetic field of strength H 0 .…”