Quasi-impulse

The quasi-impulse , crystal impulse or pseudo-impulse has nothing to do with the classic impulse of a moving mass , but describes the amount with which ( wave-like ) quasiparticles such as phonons or magnons enter the law of conservation of momentum .

Phonons, for example, are elastic oscillations of atoms around their rest position in a crystal lattice ; since all atoms vibrate in different directions at a fixed point in time, the crystal as a whole has no momentum.

The quasi-momentum of a wave can be calculated from the wave vector using the De Broglie relationship : ${\displaystyle {\vec {k}}}$

${\displaystyle {\vec {p}}=\hbar {\vec {k}}}$

with Planck's reduced quantum of action ${\displaystyle \hbar .}$

Web links

Quasiimpuls - Lexicon of Physics