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Landau theory
About: Landau theory is a research topic. Over the lifetime, 2882 publications have been published within this topic receiving 57078 citations.
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TL;DR: In this article, the authors defined the scattering amplitude of an impurity or phonon for a quasi-particle including all many-body corrections, and the definition was shown to be consistent with the fundamental diagrammatic calculation of the resistivity and with the scattering potential determining the shape of the Fermi surface.
Abstract: When setting up the theory of the transport properties of metals in terms of Landau's theory of quasi-particles, it is necessary to define precisely what is the scattering amplitude of an impurity or phonon for a quasi-particle including all many-body corrections. This is done, and the definition shown to be consistent with the fundamental diagrammatic calculation of the resistivity and with the scattering potential determining the shape of the Fermi surface. The limit of long wavelengths is evaluated in particular, and the results shown to be derivable also by a simple-minded application of the Landau theory. Both the coulomb repulsion and the interaction via virtual phonons are considered. In fact, all phonon effects cancel out from the resistivity and the band structure, a result depending on the special nature of the interaction which we discuss also from the point of view of the Landau theory.
50 citations
TL;DR: In this article, an extension to the phenomenological thermodynamic Landau-Devonshire theory was proposed to include the contribution of inhomogeneous strains caused by lattice defects to the Gibbs free energy.
Abstract: We propose an extension to the phenomenological thermodynamic Landau-Devonshire theory to include the contribution of inhomogeneous strains caused by lattice defects to the Gibbs free energy. The model yields correction terms for dielectric and ferroelectric quantities as a function of both elastic misfit strain and defectrelated strain that can be measured by x-ray-diffraction techniques. We compare the correction in Curie-Weiss temperature due to elastic and inhomogeneous strain in pristine, W and Mn 1% doped Ba 0.6Sr0.4TiO3 thin films grown on the LaAlO3 substrate. If the contribution of inhomogeneous strain is included, the agreement with measurements markedly improves.
50 citations
TL;DR: In this paper, the disappearance of ferroelectricity in thin films is discussed in the framework of the Landau theory, and the polarization profiles, the average energy density and the average polarization, which depend on the film thickness, are analyzed.
Abstract: The disappearance of ferroelectricity in thin films is discussed in the framework of the Landau theory. The way in which ferroelectricity is lost with decreasing film thickness has the properties of a phase transition. The polarization profiles, the average energy density and the average polarization, which depend on the film thickness, are analytically obtained for various boundary conditions.
50 citations
TL;DR: In this paper, the authors show that the Landau theory of phase transitions is equivalent to the theory of the mean (molecular, self-consistent) field, and that the contributions of the long-wave fluctuations are small enough.
Abstract: The Landau theory of phase transitions1 is known to ignore (in its main approximation) long-wave fluctuations of the order parameter. In this aspect this theory is equivalent to the theory of the mean (molecular, self-consistent) field. True, starting from the Landau theory one can calculate contributions of the long-wave fluctuations as well but only if the contributions are small enough. This is not the case in the immediate vicinity of a second-order phase transition. At present the fluctuation theory of phase transitions, or more specifically, the scaling1,2 or renormalization group3-5 theory, is widely used for this region
50 citations