Hybrid electromagnetic-spin oscillations in layered structures with uniaxial hexaferrites

Spectra of magnetostatic oscillations in layered dielectric-ferrite-metal structures are studied theoretically and experimentally. Hybridization of the magnetostatic oscillations and dielectric resonant modes is experimentally investigated both under saturation and in the domain region in the presence of a cylindrical magnetic domain. The experiments are performed on the platelets of magnetoplumbite, as well as barium and strontium hexaferrites. In composite structures, quartz platelets of various thicknesses are used as dielectrics.     

Effect of the Fermi surface shape on the de Haas-van Alphen oscillations in layered conductors

In this paper, we theoretically analyze the effects of the Fermi surface (FS) shape on the magnetic oscillations in quantizing magnetic fields in quasi-two-dimensional layered conductors. The theory is developed based on a phenomenological model for the electron energy spectra introduced in the paper. The model enables various Fermi surface profiles to be taken into consideration; this gives it an advantage over the commonly used tight-binding approximation. It is shown that, when the FS curvature becomes zero at an effective cross-section with maximum/minimum cross-sectional area, this can significantly affect the amplitude, shape, and phase of the oscillations, as well as the field dependence of the amplitude. The text was submitted by the author in English.     

Parametric oscillations in a whispering gallery resonator

We demonstrate strongly nondegenerate optical continuous-wave parametric oscillations in crystalline whispering gallery mode resonators fabricated from LiNbO3. The required phase matching is achieved by geometrical confinement of the modes in the resonator.     

Eigen electromagnetic oscillations in the waveguide-dielectric resonator with two-layer filling

The method of the solution problem on the eigen oscillations spectrum of electromagnetic field in the waveguide-dielectric resonator with the two-layer dielectric element was presented. The numerical calculations of the resonance frequencies for theHE ₁₁₁-,E ₀₁₁- andH ₀₁₁-oscillations types in the investigated structure were performed. The calculation results were correlated with experimental data.     

Excitation of shear waves due to the interband absorption of laser radiation in a piezoelectric semiconductor-dielectric layered structure

Optical piezoelectric generation of shear bulk acoustic waves by volume-distributed electric fields in the vicinity of a hard planar interface between a piezoelectric semiconductor and a dielectric is described theoretically. Nonstationary and nonuniform electric fields are formed as a result of the spatial separation of electrons and holes photoexcited in the piezoelectric semiconductor due to the interband absorption of laser radiation. Frequency regions where the efficiency of the optical piezoelectric excitation of shear waves increases when the surface of the piezoelectric semiconductor is loaded by another piezoelectric with a high acoustic impedance are found. Numerical estimates of the applicability of the immobile hole model are presented.     

Photothermoacoustic oscillations in a solid-piezoelectric layered structure

Photothermoacoustic oscillations in a thin plane-layered structure consisting of an isotropic solid and a piezoelectric crystal of class 6mm (or piezoelectric ceramics) are studied theoretically and experimentally. Expressions for the potential difference across an arbitrary layer of the piezoelectric transducer are derived. For the case of a two-layer transducer, the amplitude-frequency and phase-frequency dependences of the signal are analyzed. It is shown that, from these experimental dependences, one can determine certain elastic and thermal parameters of a solid. An experiment is performed with samples of Cu, Zn, and TsTS-19 piezoceramics in the frequency range within 9–1000 Hz. The experimental data are used to determine the values of the reduced Young’s modulus and the thermal diffusivity of the materials under study.     

High-Q oscillations in a layered elastic medium

Conditions of the existence of long-lived acoustic resonances that occur in a layered medium because of its oscillation with low damping factors are considered. A priori theoretical estimates relating the distribution of resonance frequencies in the complex plane to the parameters of inhomogeneity of the layered system are obtained. A scheme of resonance calculations in numerical modeling is described. Examples of geophysical media with long-lived resonances are presented.     

Friedell oscillations in a layered electron gas

The oscillations appearing in the potential of a layered electron gas in the random phase approximation are investigated for arbitrary plane distances. Due to the two-dimensional Fermi sphere, they turn out to be always of two-dimensional character, in contrast to the three-dimensional screening behaviour of the system.     

Electromagnetic waves and oscillations in the layered semiconductor-dielectric-semiconductor structure

Theoretical and numerical studies of the electromagnetic properties of the layered semiconductor — dielectric — semiconductor (SDS) structure was carried out. It was shown that the weak damping guide and surface waves may exist in this structure and retardation of surface waves may be several times more than for the semiconductor — dielectric (SD) interface. If this structure contains reflections it leads to the formation of high Q-factor resonance oscillations. It was found that at the beginning of intermode coupling of two surface oscillations in the studied resonance structure, hybrid surface oscillations with near resonance frequencies are formed. Their electromagnetic field components along the wave propagation direction are orthogonal to each other and modulated along the SD interface by orthogonal envelopes.     

Magnetic-breakdown oscillations of the thermoelectric field in layered conductors

We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev–Heisenberg model proposed for A₂IrO₃ (A = Li, Na) compounds. The spin-wave excitation spectrum, the sublattice magnetization, and the transition temperatures are calculated in the random phase approximation for four different ordered phases observed in the parameter space of the model: antiferromagnetic, stripe, ferromagnetic, and zigzag phases. The Néel temperature and temperature dependence of the sublattice magnetization are compared with the experimental data on Na₂IrO₃.     

Observation of magnetoplasma type surface polaritons on n-InSb

Surface polariton dispersion curves have been obtained for an n-InSb—air interface in a magnetic field using the ATR method and are found to be in qualitative agreement with theory. In particular the curves show the predicted non-reciprocal nature of the surface polariton propagation, and the appearance of virtual excitation type branches of the dispersion curves. On the basis of data obtained in zero magnetic field on etched surfaces, the quantitative differences between experimental and theoretical dispersion curves are attributed to surface damage.     

Ferrite-ferroelectric layered resonator with electrical and magnetic control

The principle of the design of devices with the double electrical and magnetic control that are based on a ferromagnetic resonator structure coupled with a slotline containing a ferroelectric film is considered. The effective hybridization of the magnetostatic surface wave and the slot mode is demonstrated.     

Properties of optical resonator with a layered metamaterial

The properties of longitudinal and transverse modes of an open optical resonator containing layers of a metamaterial with negative refractive index are studied. Due to the presence of these layers, the metaresonator acquires unique properties compared to a conventional open resonator. Eigenmodes of the metaresonator are studied in which the properties depend on the average dispersion and the average diffraction, which may be either positive, negative, or zero. The conditions of the existence and profiles of the waveguiding modes are obtained. The resonator with zero average diffraction is of particular interest. It is shown that, in this case, the waveguiding mode may have an arbitrary amplitude profile. Under these conditions, the discrete set of the transverse modes becomes continuous, and the eigenfrequencies become independent of the transverse amplitude profile. The resonator’s stability conditions are derived based on the ray-matrix method and diffraction theory. It is shown that insertion of a metamaterial into the resonator substantially affects the region of stability and existence of the waveguiding modes. In particular, the unstable empty resonator can thus be rendered stable.     

Surface acoustic oscillations in a periodically layered medium

The existence of surface acoustic waves at the interface between a periodically layered and a homogeneous half-space is predicted. The reason for the arisal of such waves is the violation of the transnational symmetry pertinent to the periodic structure. The properties of the surface waves at a free boundary and a boundary with an elastic half-space are considered.     

Radiation due to Josephson oscillations in layered superconductors

We derive the power of direct radiation into free space induced by Josephson oscillations in intrinsic Josephson junctions of layered superconductors. We consider the superradiation regime for a crystal cut in the form of a thin slice parallel to the c axis. We find that the radiation correction to the current-voltage characteristic in this regime depends only on crystal shape. We show that at a large number of junctions oscillations are synchronized providing high radiation power and efficiency in the terahertz frequency range. We discuss the crystal parameters and bias current optimal for radiation power and crystal cooling.     

Modified surface redshift of pulsars produced by magnetoplasma

The propagation of photons in the magnetoplasma medium of pulsar magnetosphere is studied in the framework of an effective metric theory. It is found that the surface redshift is induced by two factors: one coming from the gravitational field and another from the magnetoplasma. The magnetoplasma can shift the spectrum, and the modification of surface redshift of pulsars due to associated magnetoplasma can be the same extent as the gravitational redshift in particular cases via calculation.