Dirac point in the photon dispersion relation of a negative/zero/positive-index plasmonic metamaterial

2011 ◽  
Vol 84 (4) ◽  
Author(s):  
Vassilios Yannopapas ◽  
Alexandros Vanakaras
Keyword(s):  
Dispersion Relation ◽  
Dirac Point ◽  
Positive Index

scholarly journals Guided modes near the Dirac point in negative-zero-positive index metamaterial waveguide

2010 ◽  
Vol 18 (12) ◽  
pp. 12779 ◽  
Author(s):  
Ming Shen ◽  
Lin-Xu Ruan ◽  
Xi Chen
Keyword(s):  
Dirac Point ◽  
Metamaterial Waveguide ◽  
Guided Modes ◽  
Positive Index

scholarly journals Topological features without a lattice in Rashba spin-orbit coupled atoms

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Valdés-Curiel ◽  
D. Trypogeorgos ◽  
Q.-Y. Liang ◽  
R. P. Anderson ◽  
I. B. Spielman
Keyword(s):  
Dispersion Relation ◽  
Dirac Point ◽  
Electrical Current ◽  
Chern Number ◽  
Matter Wave ◽  
Topological Order ◽  
Spin Orbit ◽  
Topological Features ◽  
Rashba Spin ◽  
Wide Range

AbstractTopological order can be found in a wide range of physical systems, from crystalline solids, photonic meta-materials and even atmospheric waves to optomechanic, acoustic and atomic systems. Topological systems are a robust foundation for creating quantized channels for transporting electrical current, light, and atmospheric disturbances. These topological effects are quantified in terms of integer-valued ‘invariants’, such as the Chern number, applicable to the quantum Hall effect, or the $${{\mathbb{Z}}}_{2}$$ Z 2 invariant suitable for topological insulators. Here, we report the engineering of Rashba spin-orbit coupling for a cold atomic gas giving non-trivial topology, without the underlying crystalline structure that conventionally yields integer Chern numbers. We validated our procedure by spectroscopically measuring both branches of the Rashba dispersion relation which touch at a single Dirac point. We then measured the quantum geometry underlying the dispersion relation using matter-wave interferometry to implement a form of quantum state tomography, giving a Berry’s phase with magnitude π. This implies that opening a gap at the Dirac point would give two dispersions (bands) each with half-integer Chern number, potentially implying new forms of topological transport.

Semi-Dirac Points in Phononic Crystals

2014 ◽  
Author(s):  
Xiujuan Zhang ◽  
Ying Wu
Keyword(s):  
Dispersion Relation ◽  
Acoustic Wave ◽  
Wave Velocity ◽  
Dirac Point ◽  
Phononic Crystal ◽  
Effective Medium ◽  
Phononic Crystals ◽  
The Other ◽  
Dirac Cone ◽  
Topological Transition

A semi-Dirac cone refers to a peculiar type of dispersion relation that is linear along the symmetry line but quadratic in the perpendicular direction. It was originally discovered in electron systems, in which the associated quasi-particles are massless along one direction, like those in graphene, but effective-mass-like along the other. It was reported that a semi-Dirac point is associated with the topological phase transition between a semi-metallic phase and a band insulator. Very recently, the classical analogy of a semi-Dirac cone has been reported in an electromagnetic system. Here, we demonstrate that, by accidental degeneracy, two-dimensional phononic crystals consisting of square arrays of elliptical cylinders embedded in water are also able to produce the particular dispersion relation of a semi-Dirac cone in the center of the Brillouin zone. A perturbation method is used to evaluate the linear slope and to affirm that the dispersion relation is a semi-Dirac type. If the scatterers are made of rubber, in which the acoustic wave velocity is lower than that in water, the semi-Dirac dispersion can be characterized by an effective medium theory. The effective medium parameters link the semi-Dirac point to a topological transition in the iso-frequency surface of the phononic crystal, in which an open hyperbola is changed into a closed ellipse. This topological transition results in drastic change in wave manipulation. On the other hand, the theory also reveals that the phononic crystal is a double-zero-index material along the x-direction and photonic-band-edge material along the perpendicular direction (y-direction). If the scatterers are made of steel, in which the acoustic wave velocity is higher than that in water, the effective medium description fails, even though the semi-Dirac dispersion relation looks similar to that in the previous case. Therefore different wave transport behavior is expected. The semi-Dirac points in phononic crystals described in this work would offer new ways to manipulate acoustic waves with simple periodic structures.

Tunable band gap near the Dirac point in nonlinear negative-zero-positive index metamaterial waveguide

2011 ◽  
Vol 83 (4) ◽  
Author(s):  
Ming Shen ◽  
Linxu Ruan ◽  
Xinglin Wang ◽  
Jielong Shi ◽  
Qi Wang
Keyword(s):  
Band Gap ◽  
Dirac Point ◽  
Metamaterial Waveguide ◽  
Positive Index ◽  
Tunable Band Gap

Nonlinear surface waves near the Dirac point in negative–zero–positive index metamaterial

2010 ◽  
Vol 12 (8) ◽  
pp. 085201 ◽  
Author(s):  
Ming Shen ◽  
Lin-Xu Ruan ◽  
Xi Chen ◽  
Jie-Long Shi ◽  
Hai-Xia Ding ◽  
...  
Keyword(s):  
Surface Waves ◽  
Dirac Point ◽  
Nonlinear Surface Waves ◽  
Nonlinear Surface ◽  
Positive Index

Graphene–polyimide-integrated metasurface for ultrasensitive modulation of higher-order terahertz fano resonances at the Dirac point

2021 ◽  
pp. 150182
Author(s):  
Maosheng Yang ◽  
Tengteng Li ◽  
Ju Gao ◽  
Xin Yan ◽  
Lanju Liang ◽  
...  
Keyword(s):  
Dirac Point ◽  
Higher Order ◽  
Fano Resonances
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