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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 apply the Landau theory of phase transitions to the case of a direct isotropic to smectic-E transition and show that the coupling of the order parameters has crucial influence on the phase behavior and the order of the transition.
12 citations
TL;DR: In this paper, a combination of basic heat transfer relations was used to model the temperature variation in the ferroelectric as a function of time and a modified Landau formalism was calculated to calculate the polarization profile due to the temperature gradient.
12 citations
TL;DR: In this article, the influence of radiation defects on the phase transition in ferroelectric crystals was studied by calorimetric experiments and the specific heats of TGSe and DTGSe were measured.
12 citations
01 Jan 1974
TL;DR: In this paper, anharmonic lattice dynamical treatment of these effects is used to show that within the framework of a Landau theory quasi-elastic scattering is expected both above and below Tc at some phase transitions, while at others only below T c. The importance of these critical fluctuations may be assessed with the techniques of renormalization group theory.
Abstract: Experimental measurements of light and neutron scattering in materials which undergo displacive structural phase transitions have shown that there is frequently quasi-elastic response in addition to the scattering predicted by the soft mode theory. These measurements are reviewed and the phenomenological theory described. The anharmonic lattice dynamical treatment of these effects is used to show that within the framework of a Landau theory quasi-elastic scattering is expected both above and below Tc at some phase transitions, while at others only below Tc. If critical fluctuations cause a breakdown of the Landau theory close to Tc, then additional quasi-elastic scattering may be expected. The importance of these critical fluctuations may be assessed with the techniques of renormalization group theory.
12 citations
TL;DR: The model presented herein is overly simplified and ignores many of the complex interactions in real ferroelectrics; however, this model reveals an important insight: the polarization catastrophe phenomenon that is required to describe the onset of ferroelectricity naturally leads to the thermodynamic instability that is negative capacitance.
Abstract: The Landau theory of phase transitions predicts the presence of a negative capacitance in ferroelectric materials based on a mean-field approach. While recent experimental results confirm this prediction, the microscopic origin of negative capacitance in ferroelectrics is often debated. This study provides a simple, physical explanation of the negative capacitance phenomenon—i.e., ‘S’-shaped polarization vs. electric field curve—without having to invoke the Landau phenomenology. The discussion is inspired by pedagogical models of ferroelectricity as often presented in classic text-books such as the Feynman lectures on Physics and the Introduction of Solid State Physics by Charles Kittel, which are routinely used to describe the quintessential ferroelectric phenomena such as the Curie-Weiss law and the emergence of spontaneous polarization below the Curie temperature. The model presented herein is overly simplified and ignores many of the complex interactions in real ferroelectrics; however, this model reveals an important insight: The polarization catastrophe phenomenon that is required to describe the onset of ferroelectricity naturally leads to the thermodynamic instability that is negative capacitance. Considering the interaction of electric dipoles and saturation of the dipole moments at large local electric fields we derive the full ‘S’-curve relating the ferroelectric polarization and the electric field, in qualitative agreement with Landau theory.
12 citations