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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 ]
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.
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.
The two phonons have opposite wave vectors k and -k (they will propagate in opposite directions) and a frequency two times smaller than that of the photon. [1] Parametric pumping techniques can be performed in several media: [1] In piezoelectric crystals, a nonlinear piezoelectric effect will produce a modulation of fractions of a percent.
Indices which have hats are called Dirac indices, and are the set of dotted and undotted, or chiral and anti-chiral, indices. For example, if =,, ˙ = ˙, ˙ then a spinor in the chiral basis is represented as
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.
In quantum field theory, a chiral gauge theory is a quantum field theory with charged chiral (i.e. Weyl) fermions. For instance, the Standard Model is a chiral gauge theory. For topological reasons, chiral charged fermions cannot be given a mass without breaking the gauge symmetry, which will lead to inconsistencies unlike a global symmetry.
In crystals that are symmetric under inversion and time reversal, ... phonons, polaritons and ... "Weyl semimetals, Fermi arcs and chiral anomaly".