Elementary Steps on the 4He Crystal Interface Probed by 3He Atoms

The growth dynamics of c facets, governed by individual Frank-Read type of sources, has been studied at millikelvin temperatures in the presence of small concentrations of 3He atoms in the liquid. We find that in the spiral growth regime, interaction of 3He atoms with moving elementary steps on the surface results in additional friction. Our results are compared with theory, where high-frequency (ω ≥ T/ℏ) zero-point oscillations of the steps are taken into account. There is a good agreement if we assume the amplitude of these oscillations ξ ≈ 5 nm.Peer reviewe