Search results for "Ginzburg–Landau theory"
showing 10 items of 11 documents
Domain-Enhanced Interlayer Coupling in Ferroelectric/Paraelectric Superlattices
2004
We investigate the ferroelectric phase transition and domain formation in a periodic superlattice consisting of alternate ferroelectric (FE) and paraelectric (PE) layers of nanometric thickness. We find that the polarization domains formed in the different FE layers can interact with each other via the PE layers. By coupling the electrostatic equations with those obtained by minimizing the Ginzburg-Landau functional we calculate the critical temperature of transition Tc as a function of the FE/PE superlattice wavelength and quantitatively explain the recent experimental observation of a thickness dependence of the ferroelectric transition temperature in KTaO3/KNbO3 strained-layer superlatti…
Diffusion stabilizes cavity solitons in bidirectional lasers
2009
We study the influence of field diffusion on the spatial localized structures (cavity solitons) recently predicted in bidirectional lasers. We find twofold positive role of the diffusion: 1) it increases the stability range of the individual (isolated) solitons; 2) it reduces the long-range interaction between the cavity solitons. Latter allows the independent manipulation (writing and erasing) of individual cavity solitons.
Properties of Thin Ferroelectric Film with Different Electrodes
2008
The influence of different metallic and semiconducting electrodes on the properties of thin ferroelectric films is considered within the framework of the phenomenological Ginzburg-Landau theory. Allowing for the effect of charge screening in metals and semiconductors, the contribution of electric field produced by charges in the electrodes is included into the functional of free energy and, hence, to the Euler-Lagrange equation for film polarization. Application of variational method to this equation solution permitted the transformation of the free energy functional into a conventional type free energy with a renormalized coefficient before P 2 , the coefficient being dependent on the both…
Depolarization Field in Thin Ferroelectric Films With Account of Semiconductor Electrodes
2005
Within the framework of the phenomenological Ginzburg-Landau theory influence of semiconductor electrodes on the properties of thin ferroelectric films is considered. The contribution of the semiconductor electrodes with different Debye screening length of carriers is included in the functional of free energy. The influence of highly doped semiconductor electrodes on the depolarization field and the film properties was shown to be great.
Influence of semiconducting electrodes on properties of thin ferroelectric films
2005
The influence of semiconducting electrodes on the properties of thin ferroelectric films is considered within the framework of the phenomenological Ginzburg-Landau theory. The contribution of the electric field produced by charges in the electrodes allowing for the screening length of the carriers is included in the functional of the free energy and so in the Euler-Lagrange equation for the film's polarization. Application of the variational method to the solution of this equation allows the transformation of the free energy functional into a conventional type of free energy with renormalized coefficients. The obtained dependence of the coefficients on the film thickness, temperature, elect…
Semiadiabatic High-Field Polarization Response in Ferroelectrics I: Hysteresis and Nonlinear Susceptibility
2004
Ginzburg-Landau theory for ferroelectric phase instability is combined with Langevin, Fokker-Planck and imaginary time Schrodinger equation techniques to model impact of thermal noise in the kinetics of ferroelectric polarization. The proposed real space/real time numerical method allows to efficiently simulating relaxation, dynamic hysteresis and general dielectric response.
Surface-directed spinodal decomposition: Lattice model versus Ginzburg-Landau theory
2009
When a binary mixture is quenched into the unstable region of the phase diagram, phase separation starts by spontaneous growth of long-wavelength concentration fluctuations ("spinodal decomposition"). In the presence of surfaces, the latter provide nontrivial boundary conditions for this growth. These boundary conditions can be derived from lattice models by suitable continuum approximations. But the lattice models can also be simulated directly, and thus used to clarify the conditions under which the Ginzburg–Landau type theory is valid. This comparison shows that the latter is accurate only in the immediate vicinity of the bulk critical point, if thermal fluctuations can also be neglecte…
General interpolation scheme for thermal fluctuations in superconductors
2006
We present a general interpolation theory for the phenomenological effects of thermal fluctuations in superconductors. Fluctuations are described by a simple gauge invariant extension of the gaussian effective potential for the Ginzburg-Landau static model. The approach is shown to be a genuine variational method, and to be stationary for infinitesimal gauge variations around the Landau gauge. Correlation and penetration lengths are shown to depart from the mean field behaviour in a more or less wide range of temperature below the critical regime, depending on the class of material considered. The method is quite general and yields a very good interpolation of the experimental data for very…
Notes on the Electroelastic Interaction in Joint Hamiltonian and Stochastic Treatment of Polarization Response
2008
Conventional Landau theory for ferroelectric phase instability is extended by entities accounting for the violation of thermodynamic equilibrium and the impact of thermal fluctuations. The physical content concerns Ginzburg-Landau type model Hamiltonians assigned to the mean field interaction of macroscopically small and microscopically large lattice cells affected by thermal fluctuations. A special topic derived in a systematic way is long range electroelastic interaction formally given by selfconsistent solution of the polarization and strain fields. Test solution for inhomogeneous strain in a slab is presented within the framework of lattice cell picture.
Spatiotemporal optical solitons in nonlinear dissipative media: From stationary light bullets to pulsating complexes
2007
Nonlinear dissipative systems display the full (3+1) D spatiotemporal dynamics of stable optical solitons. We review recent results that were obtained within the complex cubic-quintic Ginzburg-Landau equation model. Numerical simulations reveal the existence of stationary bell-shaped (3+1) D solitons for both anomalous and normal chromatic dispersion regimes, as well as the formation of double soliton complexes. We provide additional insight concerning the possible dynamics of these soliton complexes, consider collision cases between two solitons, and discuss the ways nonstationary evolution can lead to optical pattern formation. © 2007 American Institute of Physics.