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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 paper, a family tree of perovskite-type layer materials with organic ions and the symmetry types of the lattice vibrations are derived by standard group theoretical methods, and special emphasis is given to the possibility of soft or condensating modes in the phase transitions involved.
Abstract: Starting with the 'family tree' which shows the group-subgroup relations between the various structural phases of perovskite-type layer materials with organic ions, the symmetry types of the lattice vibrations and, for some selected cases, the symmetry coordinates are derived by standard group theoretical methods. Special emphasis is given to the possibility of soft or condensating modes in the phase transitions involved and to the applicability of the Landau theory of phase transitions.
42 citations
TL;DR: In this article, an analytical solution to the two-parabola Landau model applied to melting of metal particles with sizes in the nanoscale range is presented, and the results provide an analytical understanding of the recently observed pseudo-crystalline phase of nanoscales.
Abstract: We present an analytical solution to the two-parabola Landau model, applied to melting of metal particles with sizes in the nanoscale range. The results provide an analytical understanding of the recently observed pseudo-crystalline phase of nanoscale Sn particles. Liquid skin formation as a precursor of melting is found to occur only for particles with radii greater than an explicitly given critical radius. The size dependences of the melting temperature, and of the latent heat, have been calculated, and a quantitative agreement is found with the experiment on tin particles.
42 citations
TL;DR: In this article, the critical behavior near the centers of the two lowest Landau levels and its dependence on the correlation length of the disorder potential are studied for quasi-one-dimensional systems.
Abstract: For a model of noninteracting electrons in a disorder potential under quantum Hall conditions the critical behavior near the centers of the two lowest Landau levels and its dependence on the correlation length of the disorder potential are studied. The localization length is calculated numerically for quasi-one-dimensional systems. Finite-size scaling is used to obtain the critical exponent. For the lowest Landau level universal one-parameter scaling independent of the correlation length is found. Universality in the higher Landau levels is established by an argument based on the shape of the potential matrix elements in the limit of large correlation length. In the second lowest Landau-level universality is explicitly demonstrated by comparison of numerical data obtained for a correlation length equal to the magnetic length with those obtained for the lowest Landau level. However, no scaling behavior could be found for short correlation lengths in the first Landau level.
42 citations
TL;DR: In this paper, a general Landau model for the coupled orientational and translational order parameters and including the tilt angle was proposed to describe the smectic C-isotropic phase transition.
Abstract: We propose a Landau model to describe the smectic C–isotropic phase transition. A general Landau theory for the coupled orientational and translational order parameters and including the tilt angle is developed. The conditions for the smectic C–isotropic phase transition and the stability conditions of the smectic C phase are calculated. On the basis of this model it is argued that the smectic C–isotropic phase transition is always first order. We present a detailed analysis of the question under which conditions a direct smectic C–isotropic phase transition prevails in comparison to smectic A–isotropic and nematic–isotropic transitions. The theoretical results are found to be in qualitative agreement with all published experimental results.
42 citations
TL;DR: In this paper, a tricritical point is observed in the Nd1−xSrxMnO3 (NSMO) (x=0.33) manganites at x = 0.33 which separates the first-order transition in NSMO-0.3 and second order transition of NSMO -0.4, and the contribution to the free energy from the presence of correlated clusters are strongly influencing the magnetocaloric effect.
Abstract: A tricritical point is observed in the Nd1−xSrxMnO3 (NSMO) (x=0.3, 0.33, and 0.4) manganites at x=0.33 which separates the first-order transition in NSMO-0.3 and second order transition in NSMO-0.4. The ferromagnetic transition of these compounds is further investigated by measuring magnetocaloric effect (MCE) and by applying a theoretical model based on Landau theory of phase transitions. Results indicate that the contributions to the free energy from the presence of correlated clusters are strongly influencing the MCE by coupling with the order parameter around the Curie temperature.
41 citations