Bootstat 2021: Conformal bootstrap and statistical models

Introduction to structural phase transitions

17 mai 2021, 16:30

1h

Institut Pascal, Orsay, France & online

Lecture / lecture series

Orateur

Pierre Toledano (Université de Picardie)

Description

1. Basic concepts of the Landau theory. Critical behaviour. Symmetry of the order parameter. Secondary order parameters. Specificity of first-order transitions. Useful rules for applying the theory. Construction of phase diagrams involving phase transitions.

2. Application of the theory to illustrative examples of structural transitions induced by a single irreducible representation. Transitions induced by several order parameters. Order parameter replication. Incommensurate phase transitions. Analysis of the applicability of the Landau theory to structural transitions in real systems.

3. Analysis of the critical behaviour of structural transitions in real systems. Agreement and disagreement with the theoretical predictions. Dependence of the critical behaviour on the effective space dimensionality, the order parameter dimension, the order parameter anisotropy, the range of the anisotropic interactions. Influence of elastic degrees of freedom. Specific critical behaviour of incommensurate structural transitions. Influence of defects on the critical behaviour.