Electroacoustic waves confined by a moving domain wall superlattice of a ferroelectric crystal

The dispersion properties of electroacoustic wave modes confined by a superlattice of uniformly moving 180° domain walls in a tetragonal ferroelectric crystal are considered. It is shown that the manifold of partial electroacoustic interfacial waves in the lattice is restricted to the first allowed band, the configuration of which in the plane of spectral variables can significantly vary under the action of the moving domain walls.     

Reflection of electroacoustic waves from a system of moving domain walls in a ferroelectric

The interaction of electroacoustic waves with a periodic domain structure formed in a tetragonal ferroelectric by a finite number of uniformly moving 180° domain walls is considered in the quasi-static approximation. It is established that the inclusion of the domain-wall motion leads to a significant modification of the reflectance spectra of electroacoustic waves according to the number, intensity, and location of the Bragg reflectance peaks.     

Localization of a transverse elastic wave in a semibounded acoustic superlattice of ferrimagnetic and superconducting layers: 3. Leaky surface modes and associated resonances

In terms of the effective medium method, conditions for the existence of leaky shear surface acoustic waves in a semibounded fine-layered magnetic superlattice consisting of ferrimagnetic and superconducting layers are determined. On this basis, the possibility of a resonance interaction between a surface elastic SH wave propagating in the magnetic superlattice and a shear bulk wave propagating in the adjacent nonmagnetic medium is investigated.     

Mode spectrum of noncollinear electroacoustic boundary-guided waves in a ferroelectric with a moving strip domain

The mode spectrum of electroacoustic boundary waves guided by a strip domain uniformly moving in a 4-mm ferroelectric is considered in the quasi-static approximation. The motion of the strip domain is found to cause the wave vector of the electroacoustic wave to be noncollinear with the guiding boundaries. The frequency dependences of the phase velocity are presented for the symmetric and antisymmetric modes of the electroacoustic wave. These dependences are compared in the reference system fixed to the strip domain and in the laboratory reference system. It is shown that, at low and moderate frequencies, the symmetric mode of the electroacoustic wave is more efficiently localized by a moving strip domain than by a single domain wall.     

电场中三层铁电超晶格的物理性质研究

基于微分算符技术的相关有效场理论研究用伊辛模型描述的铁电三层超晶格的物理性质。讨论了电场对电极矩、电极化率、热电系数等物理性质的影响。     

Long—Range Effects on the Pyroelectric Coefficient of Ferroelectric Superlattice

Long-range effects on the pyroelectric coefficient of a ferroelectric superlattice consisting of two different ferroelectric materials are investigated based on the transverse Ising model.The effects of the interfacial coupling and the thickness of one period on the pyroelectric coefficient of the ferroelectric superlattics are studied by taking into account the long-range interaction.It is found that with the increase of the strength of the long-range interaction,the pyroelectric coefficient decreases when the temperature is lower than the phase transition temperature;the mumber of the pyroelectric peaks decreases gradually and the phase transition temperature increases,It is also found that with the decrease of the interfacial coupling and the thickness of one period.the phase transition temperature and the number of the pyroelectric peaks decrease.     

Shear Surface Wave on a Moving Bloch Wall

Using Galileo's transformation for moving to the rest frame of the Bloch wall in the exchange-free magnetostatic approximation, we obtain the dispersion relation for a shear surface wave guided by a moving 180-degree domain boundary of a ferromagnetic crystal. It is found that the motion of the domain boundary has the orienting action on the wave normal of the shear surface wave and significantly changes the spectrum of forward-propagating waves in the frequency band below the scattered-field ferromagnetic resonance.     

Interaction of a shear wave with a moving domain wall in an iron garnet crystal

The boundary-value problem of the interaction of a plane monochromatic shear wave with a moving Bloch wall in an iron garnet crystal is solved in the framework of the nonexchange magnetostatic approximation on the basis of the method of phase invariants for wave problems with moving boundaries. For a shear wave incident on the domain wall, the possibility of the reflectionless birefringence is demonstrated. Numerical results illustrating the resonance properties of the magnetic subsystem are presented. It is established that, at the upper bound of the reflectionless birefringence range, the interaction of the shear wave with the domain wall manifests itself as a degenerate resonance with the solution in the form of two combined antiphase, collinearly propagating shear waves of infinitely large amplitudes, which form a zero resulting field.     

Invited review

The studies of superlattices in ferroelectric crystals have made a rapid progress since 1980s. A superlattice is composed of modulated domains on the micron scale, controllable with modern techniques. It reveals a number of novel physical properties of optical and acoustic character. In this paper, we review recent advances in developing new techniques for fabrication and characterization of ferroelectric superlattices, and in exploring new physical effects for applications. The outlook for superlattice applications is briefly described.     

Long-Range Effects on the Pyroelectric Coefficient of Ferroelectric Superlattice

Long-range effects on the pyroelectric coefficient of a ferroelectric superlattice consisting of two differentferroelectric materials are investigated based on the transverse Ising model. The effects of the interfacial coupling andthe thickness of one period on the pyroelectric coefficient of the ferroelectric superlattice are studied by taking intoaccount the long-range interaction. It is found that with the increase of the strength of the long-range interaction, thepyroelectric coefficient decreases when the temperature is lower than the phase transition temperature; the number ofthe pyroelectric peaks decreases gradually and the phase transition temperature increases. It is also found that with thedecrease of the interfacial coupling and the thickness of one period, the phase transition temperature and the number ofthe pyroelectric peaks decrease.     

Suppression of Chaos in a Bose-Einstein Condensate Loaded into a Moving Optical Superlattice Potential

We have shown that the application of modulating the secondary lattice is an efficient route to suppressing the generation of chaotic traveling waves of a Bose-Einstein Condensate with attractive interatomic interaction loaded into a moving optical superlattiee consisting of two lattices. With the Melnikov method, we obtain the optimal value of the relative phase between the two lattice harmonics for the control of chaos. We also find that the regularization route as the potential depth of the secondary lattice is varied and fairly rich, including the period-doubling bifurcations.     

Nonlinear waves in a chain of plane-parallel domain walls in ferromagnets

Taking into account the nonlinear interaction between plain domain walls (DWs) in a chain of DWs, one-and two-parameter solitons are obtained. These solitons are solitary shear waves propagating along the DW chain.     

Toward the theory of spin waves on the surface of a nanotube with a superlattice in a magnetic field

Electron spin waves on the surface of a semiconductor nanotube with a superlattice in a magnetic field have been considered. The spin-wave spectra and regions of collisionless wave damping have been found. It has been shown that the spin waves do not exhibit damping on small-radius tubes with a degenerate electron gas.     

On the interaction of a shear wave with a moving domain wall in a nonlinear response of the spin subsystem

A solution of the problem of parametric interaction between a plane monochromatic shear wave and a uniformly moving 180°-domain wall of a garnet-ferrite crystal is obtained in the exchangeless magnetostatic approximation by using the perturbation method under the conditions of a nonlinear response of the spin subsystem. It is shown that in a ferromagnetic resonance with magnetostatic oscillation of stray fields, the nonlinearity of the spin subsystem leads to the excitation of shear waves of triple frequency, which may have amplitudes comparable with that of the incident wave for oscillations doubly localized by a domain wall.     

Phase diagrams of a ferroelectric superlattice: A Green’s function technique study

A Fermi-type Green’s function method has been used to investigate the phase transition properties of a ferroelectric superlattice with two alternating materials on the basis of the transverse Ising model. By performing a higher-order decoupling to the equations of motion for the Green’s functions, the eigenfrequencies of the infinite ferroelectric superlattice are obtained. Moreover, we discuss the dependence of the phase diagrams on the interface coupling strength, the transverse field, and the thicknesses of two slabs. The comparison between the Green’s function technique and the usual mean-field approximation is illustrated.     

Effect of the mutual rectification of two electromagnetic waves with perpendicular polarization planes in a superlattice based on graphene

The effect of the mutual rectification of two electromagnetic waves with perpendicular polarization planes in a superlattice based on graphene was investigated. It was shown that, due to the nonadditive nature of the electronic spectrum of a superlattice based on grapheme, a constant term of current arises along its axes. The dependence of the constant of current density on the intensity of an electromagnetic wave is oscillatory in nature.     

A trapped wave in a ferroelectric with a moving strip domain

The existence of a shear homogeneous plane wave trapped by a strip domain moving uniformly in a tetragonal ferroelectric crystal is demonstrated. Using the nonrelativistic quasistatic approximation and a change to the moving frame of reference, the solution is obtained and the dispersion relation is derived for the spatial spectrum of the trapped wave. The uniqueness of the solution is established in the case of the multiple degeneracy of the roots of the characteristic equation when the trapped wave contains an attached wave in the strip domain. The trapped wave is shown to correspond to the antisymmetric mode of the electroacoustic wave of the strip domain at the initial point of the spectrum branch. The specific features of the spatial resonance of the trapped wave with a shear wave obliquely incident on the strip domain are considered.     

Attenuation of electromagnetic waves in a semiconductor superlattice in a magnetic field

Magnetoplasma waves and inhomogeneous (complex) waves in an infinite semiconductor superlattice in a magnetic field are studied, and dispersion curves are obtained. It is shown analytically and numerically that, in periodic structures, among inhomogeneous waves, there are many complex waves for which the imaginary part of the wave vector is greater than the real part. The effect of dissipation in a medium on the dispersion curves of magnetoplasma waves is examined. The dependence of the minimum phase velocity on the collision frequency and the magnetic field strength is studied.     

Longitudinal stark-cyclotron waves in semiconductor with a superlattice

Semiconductor with a superlattice in static electrical and magnetic fields parallel to the superlattice axis is considered. The existence of Stark-cyclotron longitudinal waves in non-local approximation is predicted.     

Giant magnetoresistance of iron-chromium superlattices at microwaves

Interaction between an rf electromagnetic field and the Fe/Cr superlattice placed in a rectangular waveguide so that a high-frequency current passes in the plane of superlattice layers is considered. The transmission coefficient versus the magnetic field strength is found at centimeter waves, and a correlation between this dependence and the field dependence of the dc magnetoresistance is established. It is shown that a change in the transmission coefficient may greatly exceed the giant magnetoresistance of the superlattice. The frequency dependence of the microwave measurements has an oscillatory character. The oscillation frequencies are analyzed in terms of wavelet transformation. Two types of oscillation periods are found to exist, one of which corresponds to the resonance of waves traveling in the superlattice along the direction parallel to the narrow wall of the waveguide.