Critical phenomena at perfect and non-perfect surfaces

TL;DR

This review explores how perfect and defective surfaces influence local critical phenomena, highlighting new developments and conditions under which surface defects impact critical behavior.

Contribution

It provides a comprehensive summary of surface criticality at perfect surfaces and analyzes the relevance of various surface defects on local critical behavior.

Findings

Most surface defects are irrelevant to critical behavior.

Certain defects can induce non-universal local critical phenomena.

New insights into surface critical dynamics and competing interactions.

Abstract

In the past perfect surfaces have been shown to yield a local critical behaviour that differs from the bulk critical behaviour. On the other hand surface defects, whether they are of natural origin or created artificially, are known to modify local quantities. It is therefore important to clarify whether these defects are relevant or irrelevant for the surface critical behaviour. The purpose of this review is two-fold. In the first part we summarise some of the important results on surface criticality at perfect surfaces. Special attention is thereby paid to new developments as for example the study of surface critical behaviour in systems with competing interactions or of surface critical dynamics. In the second part the effect of surface defects (presence of edges, steps, quenched randomness, lines of adatoms, regular geometric patterns) on local critical behaviour in semi-infinite systems and in thin films is discussed in detail. Whereas most of the defects commonly encountered are shown to be irrelevant, some notable exceptions are highlighted. It is shown furthermore that under certain circumstances non-universal local critical behaviour may be observed at surfaces.