Roughening Induced Deconstruction in (100) Facets of CsCl Type Crystals

TL;DR

This paper investigates the phase transitions in (100) facets of CsCl crystals using a vertex model, revealing complex interactions between roughening and reconstruction influenced by a loop-gas line.

Contribution

It demonstrates that roughening and reconstruction transitions cannot cross the loop-gas line under weak interactions and uncovers their merging with strong coupling effects.

Findings

Reconstruction and roughening transitions are separated by the loop-gas line under weak coupling.

The two critical lines merge along the loop-gas line with strong coupling scaling.

Surface roughness at the transition exceeds universal values, indicating additional critical fluctuations.

Abstract

The staggered 6-vertex model describes the competition between surface roughening and reconstruction in (100) facets of CsCl type crystals. Its phase diagram does not have the expected generic structure, due to the presence of a fully-packed loop-gas line. We prove that the reconstruction and roughening transitions cannot cross nor merge with this loop-gas line if these degrees of freedom interact weakly. However, our numerical finite size scaling analysis shows that the two critical lines merge along the loop-gas line, with strong coupling scaling properties. The central charge is much larger than 1.5 and roughening takes place at a surface roughness much larger than the conventional universal value. It seems that additional fluctuations become critical simultaneously.