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Questions tagged [phonons]

Collective excitations in periodic, elastic arrangements of atoms or molecules in condensed matter, like solids and some liquids. They are quasiparticle quantum modes of vibration of elastic structures of interacting particles.

Collective excitations in periodic, elastic arrangements of atoms or molecules in condensed matter, like solids and some liquids. They are quasiparticle quantum modes of vibration of elastic structures of interacting particles.

391 questions
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What is the experimental evidence for quantization of lattice vibrations?

Is there any direct experiment to show the quantization of lattice vibrations?
richard
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Why must phonon-phonon interaction be anharmonic?

I'm learning about phonons and this is really interesting. Why can't I describe two phonons colliding as a harmonic oscillation? Why does it have to be anharmonic for the phonon model to work?
bodacydo
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What effects arises due to hybridisation of phonon branches?

The phonon dispersion is usually given as the vibration frequency on its momentum space. Usually, there are 3 acoustic phonon modes and 3(N-1) optical modes, where 'N' is the number of atoms in the unit cell. Usually, the optical modes appear at a…
Yumnam_G
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The meaning of phonon

I learnt that phonon is quantum something of vibration. But I cannot understand what 'phonon concentration' and 'phonon scattering' mean, and how they relate to the temperature or carrier mobility. Does it have a intuitive picture?
Q. Tang
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Why the lifetime of acoustic phonons is larger than that of optical phonons?

for example, in GaAs, the LA phonon lifetime can be ~850 ns, while LO phonon lifetime is only about 5 ps. Why such huge difference occurs? Thanks!
leftbank007
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For 1D linear chain. Why does the vibration of atom at na, u(0) is equal to it at Na, u(Na)

For 1D linear chain, a is the lattice constant, u is the displacement of every atom from the equilibrium. N is the total number of atom the boundary condition is u(0)=u(Na) but my question is why? why are they equal. why does the atom at one end of…
stalk
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Do phonons age / decay?

Photons and phonons are massless entities, if my understanding is correct. Unlike photons, phonons do not travel at the speed of light, being "excitations of a classical acoustic wave." Because aging is relative to speed, and the speed of light is…
Victor Ochoa
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Monte Carlo, Non-polar optical phonon scattering?

I have a question on electron and non-polar optical phonon scattering in GaAs. Is it allowed to consider intravalley electron non-polar optical phonon scattering in L-valley of GaAs? I found in the literature, people only consider intervalley (L to…
Mahyar
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Does the wavelength/frequency of an acoustic wave change the speed of its phonons?

The speed of sound travels at a constant, depending on the medium it travels through. As amplitude increases or decreases frequency increases or decreases inversely to maintain this relation. I am somewhat confused, however, as to if this speed…
Victor Ochoa
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Why does a phononic gas require that to reach equilibrium phonon waves need to lose momentum when colliding?

I'm learning about phonons and I read that for a phononic gas to reach equilibrium the phonon waves need to lose momentum when they collide. However in an ideal gas the momentum is always preseved. Could anyone comment on this interesting…
bodacydo
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