Brillouin zone

About: Brillouin zone is a research topic. Over the lifetime, 13849 publications have been published within this topic receiving 383077 citations.

Lattice spacing relationships and the electronic structure of H.C.P. ζ phases based on silver

Abstract: The lattice spacings of h.e.p. ζ phases in the systems Ag[sbnd]Cd, Ag[sbnd]Hg, Ag[sbnd]Ga, Ag[sbnd]In, Ag[sbnd]Sn, Ag[sbnd]Aa and Ag[sbnd]Sb have been studied by the x-ray powder mothod. The results show consistent trends in the changes of lattice spacings when plotted as functions of electron: atom ratio. These trends may be interpreted in terms of distortions of the Brillouin zone following interactions between the Fermi surface with various zone faces. The results indicate that in Ag-based alloys the overlap of Fermi electrons across the (10.0) faces of the Brillouin zone occurs in the region of e/a between 1.39 and 1.40. The influence of particular solute elements on the changes in lattice spacings may be interpreted qualitatively by considering that the band gaps in the Brillouin zone of silver are decreased by the addition of the solute element.

Effect of spin-orbit coupling on the effective-spin correlation in YbMgGaO 4

Abstract: Motivated by the recent experiments on the triangular lattice spin-liquid candidate ${\mathrm{YbMgGaO}}_{4}$, we explore the effect of spin-orbit coupling on the effective-spin correlation of the Yb local moments. We point out that the anisotropic interaction between the effective spins on the nearest-neighbor bonds is sufficient to reproduce the spin-wave dispersion of the fully polarized state in the presence of strong magnetic field normal to the triangular plane. We further evaluate the effective-spin correlation at zero magnetic field within the mean-field spherical approximation. We explicitly demonstrate that the nearest-neighbor anisotropic effective-spin interaction, originating from the strong spin-orbit coupling, enhances the effective-spin correlation at the M points in the Brillouin zone. We identify these results as strong evidence for the anisotropic interaction and strong spin-orbit coupling in ${\mathrm{YbMgGaO}}_{4}$.

Optical Constants of Metals

Abstract: A calculation of the interband contribution to the frequency dependent dielectric constant of metals is attempted based on a specific model. The frequency region near the threshold for the interband transitions is considered. Emphasis in the model is laid on the bending of the energy bands near the Brillouin zone boundary. Attention is focused on cases when the Fermi surface approaches the zone boundary or has a finite area of contact with it. The momentum matrix element is taken as constant, which is fitted so as to achieve agreement with the experimentally found dip in the dispersion curve of the extinction coefficient. The values of the square of the matrix element for the noble metals, copper, silver, and gold, which fit the experimental data of Schulz, are found to be in the ratio 0.43:0.69:0.69.

Elasticity of hydrogen to 24 GPa from single-crystal Brillouin scattering and synchrotron x-ray diffraction

Abstract: We have developed a technique for studying the elasticity of single crystals of solid hydrogen and related materials at very high pressures and used the method to determine the second-order elastic moduli of single-crystal n-type hydrogen to 24 GPa at 295 K. The method involves the measurement of acoustic velocities as a function of crystallographic direction by Brillouin scattering in a diamond anvil cell with the orientation of the single crystals determined by synchrotron x-ray diffraction. Between 6 and 24 GPa, the adiabatic bulk modulus of ${\mathrm{H}}_{2}$ increases by more than a factor of 3 and the shear modulus increases by more than a factor of 4. The acoustic anisotropy of hydrogen decreases from 11% to 6% for compressional waves and from 23% to 14% for shear waves. The data are also used to calculate thermodynamic properties of hydrogen at high pressures. By including the observed velocity anisotropy, the equation of state of ${\mathrm{H}}_{2}$ derived from Brillouin data is in agreement with previous results derived solely from x-ray diffraction.

Magnonic band structures in two-dimensional bi-component magnonic crystals with in-plane magnetization

Abstract: We investigate the magnonic band structure of in-plane magnetized two-dimensional magnonic crystals composed of cobalt dots embedded into a permalloy antidot lattice. Our analysis is based on the results of numerical calculations carried out by the plane wave method. The complex magnonic band structure found in square-lattice magnonic crystals is explained on the basis of the spin wave dispersion relations calculated in the empty lattice model. We show that four principal effects influence the formation of a magnonic band structure in planar two-dimensional bi-component magnonic crystals: a folding effect, Bragg scattering, hybridization between various spin wave modes, and a demagnetizing field. While the first two effects are found for other types of waves in periodic composites, the third one exists in an anisotropic medium and the last one is specific to spin waves propagating in magnonic crystals with magnetization in the film plane. The strong anisotropy in the dispersion relation of spin waves in thin ferromagnetic films results in the crossing and anti-crossing of the fast, Damon–Eshbach-like mode with a number of other spin waves folded to the first Brillouin zone. The demagnetizing field can induce the formation of channels for spin waves which are propagating perpendicular to the external magnetic field direction, but this property exists only in the limiting range of the thicknesses and the lattice constants of the bi-component magnonic crystals. Based on the model analysis we propose a modification of the magnonic crystal structure by changing its thickness, lattice constant and aspect ratio along the direction of the applied magnetic field to significantly modify the magnonic band structure and obtain partial magnonic band gaps.