| Abstract: | The equilibrium shape ofhcp
4He crystals has been studied at temperatures 0.05≤T≤0.7 K by means of a high precision optical interferometer. We find that the profile of the interfacial boundary, close to
an almost horizontal c-facet, has a well-defined slope discontinuity separating two angular regions with different behavior
of the surface stiffness . For surfaces tilted by an angle ϕ≤100 μrad with respect to the c-facet, we obtain , contrary to the linear angular dependence predicted by current theories. |
