Defects and Topology

Abstract

The ordered states which we considered in the preceding chapter are spatially uniform, i.e., the order parameter ψ has the same value everywhere in space. In practice, however, ψ could be a function of r on account of imperfections. Our interest here is in topological defects (like dislocations), that are related intrinsically to symmetry breaking. We shall therefore not be concerned with nontopological defects such as interstitials or substitutional impurities in crystalline solids. Topological defects comprise both singular and nonsingular configurations [4.1]. The latter are sometimes referred to as textures.