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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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40 citations
TL;DR: In this paper, the authors studied the d-wave holographic superconductors in the presence of constant external magnetic fields by using the analytic matching method and numerical computation and obtained the expression for the upper critical magnetic field up to O(κ 2 ) order.
Abstract: We study the d-wave holographic superconductors (the d-wave model proposed in (arXiv:1003.2991(hep-th))) immersed in constant external magnetic fields by using the analytic matching method and numerical computation. In the probe limit, we calculate the spatially dependent condensate solution in the presence of the magnetism and find that the expression for the upper critical magnetic field satisfies the relation given in the Ginzburg- Landau theory. The result shows that the upper critical field gradually increases to its maximum value Bc2 at absolute zero temperature T = 0, while vanishing at the critical temperature T = Tc. Moving away from the probe limit, we investigate the effect of spacetime backreaction on the critical temperature and the upper critical magnetic field. The magnetic fields as well as the electric fields acting as gravitational sources reduce the critical temperature of the superconductor and actually result in a dyonic black hole solution to the leading order. We obtain the expression for the upper critical magnetic field up to O(κ 2 ) order. The analytic result is consistent with the numerical findings.
40 citations
TL;DR: A Landau theory based on the analogous molecular-field theory for orthorhombic biaxial nematic fluids is constructed, which correctly predicts the complete set of invariants formed from the ordering tensors, and avoids ad hoc parametrization of the molecular biaXiality.
Abstract: Nematic liquid crystal phase diagrams in temperature-biaxiality space are usually complex. We construct a Landau theory based on the analogous molecular-field theory for orthorhombic biaxial nematic fluids. A formal procedure yields coefficients (some of which, unusually, can be tensorial) in this Landau expansion, correctly predicts the complete set of invariants formed from the ordering tensors, and avoids ad hoc parametrization of the molecular biaxiality. By regularizing the Landau expansion to avoid unwanted order parameter divergences at low temperatures, we predict phase behavior over the whole range of biaxiality. The resulting phase diagrams have the same topology as those of molecular-field theory.
40 citations
TL;DR: In this paper, the authors take the Landau theory of phase transitions as the basis of a simple model where the alloy consists of an homogeneous matrix interacting with a few superparamagnetic clusters.
40 citations
TL;DR: The phase diagram of ferroelastic Pb3PO42-Pb3AsO4)2 has been reinvestigated and four new phase transitions have been found from birefringence measurements at low temperatures as mentioned in this paper.
Abstract: The phase diagram of ferroelastic Pb3(PO4)2-Pb3(AsO4)2 has been reinvestigated and four new phase transitions have been found from birefringence measurements at low temperatures. The first-order phase transition between the phases b (C2/c) and c (P21/c) in Pb3(AsO4)2 becomes continuous with increasing P-content. In Pb3(P0.2As0.8O4)2, a monoclinic intermediate phase bc was identified from the measurements of the spontaneous strain, the morphic birefringence and the orientation of the optical indicatrix. The experimental results are interpreted using the Landau theory of biquadratically coupled order parameters. Phase b is related to an order parameter of L-point symmetry in the paraelastic phase a (3). The phase c is due to a critical F-point in 3. The intermediate phase bc is the consequence of the biquadratic coupling of order parameters with L-and F-point symmetry. Model calculations for Pb3(P0.2As0.8O4)2 relate the free energies of the phases b, bc and c and the temperature dependence of the o...
40 citations