Temperature dependence of facet ridges in crystal surfaces

The equilibrium crystal shape of a body-centered solid-on-solid (BCSOS) model on a honeycomb lattice is studied numerically. We focus on the facet ridge end points (FRE's). These points are equivalent to one-dimensional Kardar-Parisi-Zhang-type growth in the exactly soluble square lattice BCSOS model. In our more general context the transfer matrix is not stochastic at the FRE points, and a more complex structure develops. We observe ridge lines sticking into the rough phase where the surface orientation jumps inside the rounded part of the crystal. Moreover, the rough-to-faceted edges become first order with a jump in surface orientation, between the FRE point and Pokrovsky-Talapov (PT) type critical endpoints. The latter display anisotropic scaling with exponent z=3 instead of familiar PT value z=2.