Brillouin zone

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

Structural properties and quasiparticle energies of cubic SrO, MgO and SrTiO3

Abstract: The structural properties and the band structures of the charge-transfer insulating oxides SrO, MgO and SrTiO3 are computed both within density functional theory in the local density approximation (LDA) and in Hedin's GW -scheme for self-energy corrections, by using a model dielectric function, which approximately includes local field and dynamical effects. The deep valence states are shifted by the GW -method to higher binding energies, in very good agreement with photoemission spectra. Since in all of these oxides the direct gaps at high-symmetry points of the Brillouin zone may be very sensitive to the actual value of the lattice parameter a already at the LDA level, self-energy corrections are computed both at the theoretical and the experimental a . For MgO and SrO, the values of the energies of transition between the valence and the conduction bands are improved by GW -corrections, while for SrTiO3 they are overestimated. The results are discussed in relation to the importance of local field effects and to the nature of the electronic states in these insulating oxides.

Quasiparticle dispersion in the cuprate superconductors and the two-dimensional Hubbard model

Abstract: The momentum dispersion of the peak structure of the single-particle spectral weight A(p,\ensuremath{\omega}) of the two-dimensional Hubbard model is discussed. Using results obtained from Monte Carlo simulations on lattices up to 12\ifmmode\times\else\texttimes\fi{}12 in size, we determine the low-lying quasiparticle dispersion relation. This dispersion relation is anomalously flat near the (\ensuremath{\pi},0) and (0,\ensuremath{\pi}) points of the Brillouin zone, similar to the results of recent angular resolved photoemission measurements of the hole-doped cuprates. We argue that the generic nature of the quasiparticle dispersion relation observed in these materials arises from the strong Coulomb interaction and reflects the hole-spin correlations rather than the one-electron interactions which customarily determine the band structure.

Unique characteristic features of stimulated Brillouin scattering in small-core photonic crystal fibers

Abstract: We present extensive stimulated Brillouin scattering (SBS) results from experiments and modeling for four different photonic crystal fibers (PCFs) with core diameters ranging from 8 to 1.7 μm. These results reveal several SBS characteristic features of small-core PCFs, high thresholds, and acoustic peaks, which are due to their antiguiding nature and highly multimode acoustic character. The nature of what we believe to be new acoustic modes is examined in the light of the large variations observed in the Brillouin gain, Brillouin threshold, and Brillouin shift with decreasing core diameter and optical wavelength.

High-energy optical response of artificial opals

Abstract: A detailed experimental study of the optical properties in the high-energy region (up to $a∕\ensuremath{\lambda}=1.8$) of high-quality artificial opals is performed by means of reflection and transmission spectroscopy. A number of issues, such as scalability and finite size effects, are taken into account before tentative comparison with theory is carried out. The experimental system under study is further modified by a controlled filling of the interstitials between the spheres, and its optical properties monitored throughout the process. We observe that the main features of the optical response of artificial opals seem to be accounted for by bands originated by wave vectors parallel to the $\ensuremath{\Gamma}L$ direction and their perturbations, such as gaps opening at the center and edges of the Brillouin zone and anticrossings elsewhere, introduced through the interaction with other bands of similar energy and symmetry. This work constitutes an experimental approach to understand the interaction of light with photonic bands which introduces a challenge for future experimental and theoretical work.

Electronic structure of CaB6

Abstract: The calcium hexaboride, CaB6, is a typical semiconducting metal hexaboride. Here two self-consistent APW calculations of its electronic energy bandstructure are reported, in the muffin-tin approximation and in the warped muffin-tin approximation. In both calculations, the local-spin-density approximation is used and the relativistic effects are taken into account. The bandstructure of the muffin-tin approximation is semimetallic. The non-muffin-tin corrections in the warped muffin-tin approximation tends to cause a small, direct energy gap between the valence and conduction bands at the X points in the simple cubic Brillouin zone. The magnitude of the energy gap to 0.3 eV, in reasonable agreement with the experimental value, 0.4 eV, suggested by the temperature dependence of the electrical resistivity. The calculated result for the density of states agrees reasonably well with an experimental result for the XPS spectrum.