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Weyl spinors are a solution to the Dirac equation derived by Hermann Weyl, called the Weyl equation. [3] For example, one-half of a charged Dirac fermion of a definite chirality is a Weyl fermion. [4] Weyl fermions may be realized as emergent quasiparticles in a low-energy condensed matter system.
A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids.In the context of optically trapped objects, the quantized vibration mode can be defined as phonons as long as the modal wavelength of the oscillation is smaller than the size of the object.
An acoustic metamaterial, sonic crystal, or phononic crystal is a material designed to manipulate sound waves or phonons in gases, liquids, and solids (crystal lattices).By carefully controlling properties such as the bulk modulus β, density ρ, and chirality, these materials can be tailored to interact with sound in specific ways, such as transmitting, trapping, or amplifying waves at ...
Solids are made of only three kinds of particles: electrons, protons, and neutrons. None of these are quasiparticles; instead a quasiparticle is an emergent phenomenon that occurs inside the solid. Therefore, while it is quite possible to have a single particle (electron, proton, or neutron) floating in space, a quasiparticle can only exist ...
The three first are Type-I Weyl semimetals, the last one is a Type-II Weyl semimetal. In quantum mechanics , Dirac cones are a kind of crossing-point which electrons avoid , [ 8 ] where the energy of the valence and conduction bands are not equal anywhere in two dimensional lattice k -space , except at the zero dimensional Dirac points.
A chiral phenomenon is one that is not identical to its mirror image (see the article on mathematical chirality). The spin of a particle may be used to define a handedness, or helicity, for that particle, which, in the case of a massless particle, is the same as chirality. A symmetry transformation between the two is called parity transformation.
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Phonon polaritons only result from coupling of transverse optical phonons, this is due to the particular form of the dispersion relation of the phonon and photon and their interaction. Photons consist of electromagnetic waves, which are always transverse. Therefore, they can only couple with transverse phonons in crystals.