E. S. Syrkin

Dissipative interaction and anomalous surface absorption of bulk phonons at a two-dimensional defect in a solid.

Abstract We predict an extreme sensitivity to the dissipative losses of the resonant interaction of bulk phonons with a 2D defect in a solid. We show that the total resonant reflection of the transverse phonon at the 2D defect, described earlier without an account for dissipation, occurs only in the limit of extremely weak dissipation and is changed into almost total transmission by relatively weak bulk absorption. Anomalous surface absorption of the transverse phonon, when one half of the incident acoustic energy is absorbed at the 2D defect, is predicted for the case of “intermediate” bulk dissipation.

Capillary phenomena and elastic waves localized near a plane crystal defect

Abstract Using the concept of capillary phenomena in the theory of elasticity the problem of elastic waves, localized near a plane defect of a crystal, is considered. The spectra, polarization and depth of penetration for the three types of localized elastic waves are found. The anomalous reflection of slipping sound waves from a plane defect is also considered and the relations between peculiarities of reflection coefficients with the spectra of localized waves are obtained. A possible instability of surface elastic waves is investigated.

Resonance absorption, reflection, transmission of phonons and heat transfer through interface between two solids

The different mechanisms of resonant transport of phonons between two media in the presence of an impurity intermediate layer are described. Particular attention is focused on the resonance interaction of elastic waves with a two-dimensional defect on the contact boundary between two solids, on the multichannel interface phonon scattering, and on the experimentally observed nonmonotonic temperature dependence of the reduced heat flux. In the cases when there is a direct interaction between edge atoms of the matrix as non-nearest neighbors or when the impurities do not fill completely the 2D interface layer, an additional channel for the transmission of phonons through the interface opens. This additional transmission channel manifests itself as a transmission (or reflection or absorption) peak with an asymmetric line shape (the so-called Fano-like resonance for phonons due to interference between the two transmission channels). Some applications of the Fano-like interference phenomena in magnon heat condu...

Low-temperature phonon transport in 3D point-contacts (Review)

This review is devoted to describing nonequilibrium carrier systems and relaxational and kinetic phenomena in three-dimensional point-contacts. Attention is focused on describing a phonon system which becomes substantially modified under conditions of ballistic transport. In such systems the energy fluxes are limited by the presence of weakly coupled layers of impurity atoms, planar defects, or microscopic-size contacts. The small size of point-contacts, ranging from several to 1000 nm, makes it possible to investigate low-temperature heat and charge transfer on scales less than the characteristic inelastic scattering lengths. A mechanism of phonon transport in the presence of an interface is analyzed, and various models of a planar defect are examined. The special features of interfacial phonon transport, where the transport coefficients are determined not by scattering processes in the volume of a bulk crystal but rather by the properties of the intercrystalline boundary, are studied. The quantum phonon...

Ioffe–Regel’ crossover and boson peaks in disordered solid solutions and similar anomalies in heterogeneous crystalline structures

Low-frequency features of the phonon spectra of disordered solid solutions and heterogeneous crystalline structures are analyzed at the microscopic level. It is shown that boson-peak type excitations can arise in disordered solid solutions whose sites have only translational degrees of freedom. Thus it is established that such excitations appear mainly because of the additional positional dispersion of sound waves which is due to the disordering. The influence of boson-peak excitations on the low-temperature specific heat is investigated. It is found that in a number of cases the specific heat is more sensitive to excitations of this kind than the low-frequency density of states is. It is shown that anomalies similar to Ioffe–Regel’ crossover and boson peaks can also arise in disordered heterogeneous crystalline structures with a complicated lattice.

Atomic dynamics and the problem of the structural stability of free clusters of solidified inert gases

The dependence of the rms amplitudes of atoms in free clusters of solidified inert gases on the cluster size is investigated theoretically and experimentally. Free clusters are produced by homogeneous nucleation in an adiabatically expanding supersonic stream. Electron diffraction is used to measure the rms amplitudes of the atoms; the Jacobi-matrix method is used for theoretical calculations. A series of distinguishing features of the atomic dynamics of microclusters was found. This was necessary to determine the character of the formation and the stability conditions of the crystal structure. It wass shown that for clusters consisting of less than N∼103 atoms, as the cluster size decreases, the rms amplitudes grow much more rapidly than expected from the increase in the specific contribution of the surface. It is also established that an fcc structure of a free cluster, as a rule, contains twinning defects (nuclei of an hcp phase). One reason for the appearance of such defects is the so-called vertex in...

Partial frequency distribution functions for a multilayer crystal (illustrated by a high-temperature superconductor of 1–2–3 type)

Abstract Calculations of the partial frequency distribution functions based on the concrete model for a multilayer crystal are presented. The model chosen corresponds to a high-temperature superconductor of YBaCuO-type. These calculations are realized by the Jacobi matrix method.

Long wavelength surface oscillations of a crystal with an adsorbed monolayer

Abstract Macroscopic equations of adsorbed atom monolayer dynamics on a deformable crystal are derived. It is shown that a heavy decelerating adsorbed layer can induce two surface waves of the Rayleigh polarization. The higher-frequency one of them has the terminal point in the region of low wave numbers and changes into a pseudosurface longitudinal wave. In the case of a weakly bonded adsorbed monolayer the conditions for the appearance of weakly attenuating resonance modes are found. The situation is analysed for the case that the dispersion laws of the slow surface wave in the crystal with the adsorbed layer have the form ω∼k 1 2 typical for two-dimensional plasmons.

To the theory of rare gas alloys: heat capacity

The low-temperature heat capacity of cryocrystals containing impurity clusters is investigated theoretically and experimentally. Such defects might essentially enrich the low-frequency part of the phonon spectrum by introducing both localized and delocalized vibrations. The effect of both types of vibrations on the temperature dependence of the heat capacity is analyzed. The heat capacity of the disordered solid solution Kr–Ar (Ar concentration ∼25%) is studied as an example of the effect of the light, weakly coupled impurities on the low-temperature thermodynamic characteristics of a system. The mass defect of such an impurity induces “phonon pumping” from the low-frequency part of the spectrum into the high-frequency part and decreases the low-temperature heat capacity, while the weakened interaction between the impurity and the host atoms, combined with even weaker interaction between the impurities, leads to the formation of a low-temperature maximum on the heat capacity temperature dependence. The an...

Elastic properties and phonon spectra of quasi-two-dimensional VSe2

A recently developed method is used to make acoustic measurements of VSe2 single crystals. The components of the elastic constant tensor are determined from the data of these measurements. The experimental data are used to calculate the total and partial phonon densities of VSe2, which permit an explanation of the vibrational spectra of this compound.