Ginzburg–Landau theory

This chapter discusses the extension of the theory to allow spatial variation in the order parameter and determining the shape of the interface and the surface contribution to the free energy. It describes the size of fluctuations of the order parameter, determining whether they are sufficiently small to be ignored or whether they dominate the properties of the system and require careful treatment. It discusses Vitaly Ginzburg and Lev Landau's sophisticated model which allows the order parameter to vary in space. The chapter outlines the benefits of Ginzburg and Landau's model, which includes the description of the interface between phases and estimation of the surface free energy. It elaborates how the model predicts the existence of topological singularities in the order parameter, such as quantified vortices in superfluid systems.