Roughening Transition in theHe4Solid-Superfluid Interface

Abstract
Principal planes of the He4 solid-superfluid interface are expected to undergo roughening transitions at temperatures of about 1 K. An experiment is described in which two such transitions were observed in the hcp-superfluid interface: first for the basal plane at 1.08 K and second for an orthogonal face at 0.85 K.