Landau’s Theory of Phase Transitions
Landau’s theory concerns the kind of invariants consistent with the symmetry of the crystal that may appear in the expression for the free energy. In this sense, it should be viewed as one of the successful applications of the group theory in classical physics. Unlike ordinary classical applications, however, the representation theory for space groups plays an essential role here, because a change of crystal symmetry is the main issue. It is most interesting to note that possible types of phase transitions are determined definitely solely from symmetry considerations.
KeywordsIrreducible Representation Brillouin Zone Identity Representation Symmetry Operation Lower Eigenvalue
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- 14.1L. D. Landau, E. M. Lifshitz: Statistical Physics, Part 1, 3rd ed. (Pergamon, Oxford 1980) pp. 446–471Google Scholar
- 14.2A detailed treatment without using group theory is given by T. Nagamiya: “Helical Spin Ordering” in Solid State Physics, Vol. 20, ed. by F. Seitz, D. Turnbull, H. Ehrenreich (Academic, New York 1967) pp. 305–411Google Scholar