PHOTONIC DIRAC CONES REALIZED BY ACCIDENTAL DEGENERACY ON THE BRILLOUIN-ZONE BOUNDARY

2013 ◽  
Vol 28 (02) ◽  
pp. 1441008 ◽  
Author(s):  
KAZUAKI SAKODA
Keyword(s):  
Perturbation Theory ◽  
Group Theory ◽  
Brillouin Zone ◽  
Square Lattice ◽  
Two Dimensional ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Exact Agreement ◽  
Accidental Degeneracy ◽  
Degenerate Perturbation Theory

The condition for the formation of Dirac cones at arbitrary points in the Brillouin zone by the accidental degeneracy of two photonic bands was examined by the degenerate perturbation theory and group theory based on the spatial symmetry of two modes. The analysis was applied to a two-dimensional square-lattice photonic crystal with C4v symmetry and the dispersion relation in the vicinity of the M point was examined. Exact agreement between the analytical and numerical calculation was obtained.

Irreducible first Brillouin zone for two-dimensional magnonic crystals with asymmetric complex lattices

2021 ◽  
pp. 2150170
Author(s):  
Hui Yang ◽  
Guo-Hong Yun ◽  
Yong-Jun Cao
Keyword(s):  
Brillouin Zone ◽  
Unit Cell ◽  
Square Lattice ◽  
Two Dimensional ◽  
Area Formula ◽  
Irreducible Part ◽  
Full Band ◽  
Magnonic Crystals ◽  
Magnonic Crystal ◽  
Complex Basis

Two-dimensional (2D) magnonic crystal (MC) with an asymmetric complex basis is proposed in this paper, and its band structures are calculated in the whole area of the first Brillouin zone (BZ). This kind of MCs is composed of two different atoms in the unit cell, and the symmetry of the unit cell is broken due to changes in the position of the second atom, so the irreducible part of the BZ is no longer the small area [Formula: see text] for square lattice, and it must be expanded to the whole first BZ. Only by investigating the whole first BZ, can we get the true full band-gap for this kind of MCs.

Angular control of acoustic waves oblique incidence by phononic crystals based on Dirac cones at the Brillouin zone boundary

2018 ◽  
Vol 382 (6) ◽  
pp. 423-427 ◽  
Author(s):  
Wen-Qiang Zhang ◽  
Xin Zhang ◽  
Fu-Gen Wu ◽  
Yuan-Wei Yao ◽  
Shui-Fang Lu ◽  
...  
Keyword(s):  
Brillouin Zone ◽  
Acoustic Waves ◽  
Oblique Incidence ◽  
Phononic Crystals ◽  
Zone Boundary ◽  
Brillouin Zone Boundary

Photonic Band Structure of Nanochannel Glass Materials

1996 ◽  
Vol 431 ◽  
Author(s):  
A. Rosenberg ◽  
R. J. Tonucci ◽  
H.-B. Lin
Keyword(s):  
Band Structure ◽  
Brillouin Zone ◽  
Near Infrared ◽  
Nearest Neighbor ◽  
Dielectric Structure ◽  
Zone Boundary ◽  
Photonic Band Structure ◽  
Brillouin Zone Boundary ◽  
Photonic Band ◽  
Good Agreement

AbstractWe demonstrate that nanochannel glass (NCG) materials are ideal for investigating twodimensional (2D) photonic band-structure effects. The NCG materials we have studied consist of triangular arrays of glass cylinders embedded in a glass matrix, having center-tocenter nearest-neighbor separations from 0.54 to 1.08 μm. The indices of refraction of the two glasses differ by less than 0.02 in the relevant spectral region. Narrow attenuation features occur whenever the dispersion relation for light propagating within such a periodic dielectric structure crosses a Brillouin zone boundary. The attenuations corresponding to the first Brillouin zone appear in the near-infrared (IR), at wavelengths between 1 and 3 μm, in good agreement with calculations.

Tilt and acoustic instabilities in ABX 4, A 2 BX 4 and ABX 3 perovskite structure types: their role in the incommensurate phases of the organic–inorganic perovskites

2005 ◽  
Vol 61 (6) ◽  
pp. 616-626 ◽  
Author(s):  
Ian Peter Swainson
Keyword(s):  
Brillouin Zone ◽  
Three Dimensional ◽  
Low Frequency ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Perovskite Layer ◽  
Modulated Phases ◽  
Acoustic Instabilities ◽  
Incommensurate Phases ◽  
Zero Frequency

An examination of the tilt modes and other low-frequency modes is made for an isolated, untilted perovskite layer, which maps very simply to the ABX 4 perovskites. A sheet of pure tilts exists at the Brillouin Zone boundary at {ξ, ½, ζ}. An instability is also found at all wavevectors which can be described as continuously varying from pure tilts to pure layer displacements as a function of the wavevector. Analysis is extended by considering the stacking of layers in the I-centered A 2 BX 4-layer perovskites. The effect of freezing in the commensurate tilt required to generate the Cmca tilt system, pertinent to the modulated phases of propylammonium salts, is examined. The zero-frequency modes are restricted to two planes in the Brillouin Zone. All of the observed wavevectors associated with modulated phases, and the commensurately tilted propylammonium tetrachlorocadmate, are consistent with this calculation. The effect of full three-dimensional connectivity is briefly reviewed for the true ABX 3 perovskites. While pure tilt incommensurates appear to be hypothetically possible, they do not appear to have been observed to date.

scholarly journals Nodal Brillouin-zone boundary from folding a Chern insulator

2017 ◽  
Vol 95 (5) ◽  
Author(s):  
Li-Jun Lang ◽  
Shao-Liang Zhang ◽  
Qi Zhou
Keyword(s):  
Brillouin Zone ◽  
Zone Boundary ◽  
Brillouin Zone Boundary

Magnetic excitations at the Brillouin zone boundary in Mn (17%Fe, 3%Cu) alloy

2004 ◽  
Vol 350 (1-3) ◽  
pp. E79-E81
Author(s):  
J Jankowska-Kisielińska ◽  
K Mikke ◽  
B Hennion
Keyword(s):  
Brillouin Zone ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Magnetic Excitations ◽  
Cu Alloy
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