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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 ...
A Weyl semimetal is a solid state crystal whose low energy excitations are Weyl fermions that carry electrical charge even at room temperatures. [ 11 ] [ 12 ] [ 13 ] A Weyl semimetal enables realization of Weyl fermions in electronic systems. [ 9 ]
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 ...
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.
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.
The term chiral / ˈ k aɪ r əl / describes ... light through an achiral crystal (or metamaterial) can form an experimental arrangement that is different from its ...
Crystals found in rocks typically range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are occasionally found. As of 1999 [update] , the world's largest known naturally occurring crystal is a crystal of beryl from Malakialina, Madagascar , 18 m (59 ft) long and 3.5 m (11 ft) in ...
In crystals that are symmetric under inversion and time reversal, electronic energy bands are two-fold degenerate. This degeneracy is referred to as Kramers degeneracy . Therefore, semimetals with linear crossings of two energy bands (two-fold degeneracy) at the Fermi energy exhibit a four-fold degeneracy at the crossing point.