17 research outputs found
Dissipative Interaction and Anomalous Surface Absorption of Bulk Phonons at a Two-Dimensional Defect in a Solid
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.Comment: 11 preprint pages, no figure
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 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, the 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
resonance for phonons due to interference between the two transmission channels). Some applications of the
Fano effect in magnon heat conductivity are also discussed
Pattern formation and localization in the forced-damped FPU lattice
We study spatial pattern formation and energy localization in the dynamics of
an anharmonic chain with quadratic and quartic intersite potential subject to
an optical, sinusoidally oscillating field and a weak damping. The
zone-boundary mode is stable and locked to the driving field below a critical
forcing that we determine analytically using an approximate model which
describes mode interactions. Above such a forcing, a standing modulated wave
forms for driving frequencies below the band-edge, while a ``multibreather''
state develops at higher frequencies. Of the former, we give an explicit
approximate analytical expression which compares well with numerical data. At
higher forcing space-time chaotic patterns are observed.Comment: submitted to Phys.Rev.
Effects of phonon interference through long range interatomic bonds on thermal interface conductance
We investigate the role of two-path destructive phonon interference induced by interatomic bonds beyond the
nearest neighbor in the thermal conductance of a silicon-germanium-like metasurface. Controlled by the ratio between
the second and first nearest-neighbor harmonic force constants, the thermal conductance across a germanium
atomic plane in the silicon lattice exhibits a trend switch induced by the destructive interference of the
nearest-neighbor phonon path with a direct path bypassing the defect atoms. We show that bypassing of the
heavy isotope impurity is crucial to the realization of the local minimum in the thermal conductance. We highlight
the effect of the second phonon path on the distinct behaviors of the dependence of the thermal conductance
on the impurity mass ratio. All our conclusions are confirmed both by Green’s Function calculations for the
equivalent quasi-1D lattice models and by molecular dynamics simulations
On the self-consistent spin-wave theory of layered Heisenberg magnets
The versions of the self-consistent spin-wave theories (SSWT) of
two-dimensional (2D) Heisenberg ferro- and antiferromagnets with a weak
interlayer coupling and/or magnetic anisotropy, that are based on the
non-linear Dyson-Maleev, Schwinger, and combined boson-pseudofermion
representations, are analyzed. Analytical results for the temperature
dependences of (sublattice) magnetization and short-range order parameter, and
the critical points are obtained. The influence of external magnetic field is
considered. Fluctuation corrections to SSWT are calculated within a
random-phase approximation which takes into account correctly leading and
next-leading logarithmic singularities. These corrections are demonstrated to
improve radically the agreement with experimental data on layered perovskites
and other systems. Thus an account of these fluctuations provides a
quantitative theory of layered magnets.Comment: 46 pages, RevTeX, 7 figure
Low-frequency elastic vibrations localized near fracture in solid
Consiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal