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.

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Problem with derivation of phonons in crystal

In this derivation of phonon solutions, everywhere, we are forcefully assuming the wavelike characteristics along the length of the chain. While all we can deduce for finding out the fundamental ...
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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!
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In solids, is it phonons, or is it the oscillations of electrons in bands, that emit most of the blackbody radiation?

In solids (most any object we see), which tends to emit most of the blackbody radiation: phonons (atomic, or molecular dipole, lattice vibrations) or oscillating electrons in their energy bands?
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8 views

which unit cell to use for dynamic structure factor in neutron scattering?

I'm trying to calculate the dynamic structure factor for inelastic neutron scattering, but I get a function which doesn't obey certain symmetries of the crystal lattice and which changes depending on ...
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17 views

what is the relationship between phonon frequency and normal modes frequency in crystal

I want to know what is the relationship between phonon frequency and normal modes frequency in crystal? is the same? Thanks in advance Farrokh
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801 views

Why do phonons cause excellent heat conduction in diamonds?

Phonons are the quantum of lattice vibrations in crystals and are not to be confused with photons, the gauge bosons of the electromagnetic force. Apparently, they contribute to heat conduction, but I ...
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How is Mössbauer spectroscopy so resistant to thermal motion?

Mössbauer spectroscopy detects tiny shifts (on the order of $\mu$eV or meV) in a gamma ray's energy due to the chemical environment of the nucleus. The scan consists of moving a source of excited ...
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72 views

Is it possible to efficiently extract phonons from a lattice?

The population inversion generated in lasers occurs in multi-level atomic systems. As an example, the Nd:YAG energy diagram is shown below. The pump pushes the Nd ions up to the upper levels, and ...
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Proof of equivalence between soundwaves and phonons in large wavelength limit (Ashcroft-Mermin, ch. 22)

In chapter 22, Ashcrof and Mermin argue that the normal modes of a harmonic crystal are not only formal but precisely equal to the large wavelength limit of acoustic phonons (which sounds, of course, ...
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129 views

Force constant of metals - Kohn anomaly

In Introduction to Solid State Physics (Kittel), it assumed the force constant between plane $s$ and $s+p$ $C_p=A\frac{\sin pk_0a}{pa}$ in metals to represent a Kohn anomaly. It says such a form is ...
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105 views

How do I determine resistivity from electron defects of high purity gold?

I am trying to create a plot for the electrical resistivity of high purity gold from 1 K to 1000 K. I found gold's resistivity at 300 K using the Wiedemann-Franz Law based on thermal conductivity data ...
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23 views

Effect of Phonon Density change

I am trying to figure out the phonon density change effect on anharmonic decay of phonons. How this two phenomena could be related and what could be the possible effect in such case. Moreover ...
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24 views

should transverse and longitudinal phonon velocities be equal for this mass spring system?

Let's say we have a cubic lattice of identical masses $m$, each connected to its 6 nearest neighbors by identical spring constants $k$. Essentially, the problem is I get an eigenvalue problem with ...
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62 views

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. ...
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40 views

phonon dispersion with random masses

In order to see how phonons should be affected by disorder, I've been playing around with a model involving a 1D chain of masses linked by springs, where the spring strengths are all the same but the ...
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60 views

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 ...
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92 views

What does a 'complex displacement' of phonon mode mean?

I'm trying to interpret the phonon mode output file from a phonopy/vasp calculation, and this webpage talks about the 'complex displacement' of atoms in the system, and I'm not quite sure what it ...
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71 views

How to calculate phonon decay rate?

Here, the authors calculate the quality factor for a resonator. They take it as one over phonon decay rate, given by (24). Simplified, (24) looks like this: \begin{equation} \Gamma = \gamma_{N-1,N} - ...
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123 views

Why is the k=0 phonon neglected when calculating Debye-Waller factor?

When calculating Debye-Waller factor one gets the form: $e^{-2W} = ...
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205 views

Do I understand measurement of dispersion relation in a solid correctly?

I'm currently doing an introduction to solid state physics course and have a quick question about measurement of the dispersion relation of phonons in a solid: The way I understood it is the ...
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140 views

What is the physical meaning of group velocity for elastic waves through crystals?

In a chapter about phonons they define group speeds for elastic waves in crystals as the derivative of the dispersion relation: $$v_g = \frac{d{\omega}}{d{k}} $$ I wonder though how they come to ...
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61 views

Ballistic Conduction - Difference between Bosonic and Fermionic Transport

Ballistic Conduction is the phenomenon of an ideal conduction environment for quantum particles - for electrons the Ballistic Conduction is not infinity, but is proportional to the difference between ...
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37 views

Phonon softening explanation

Is there a simple, intuitive answer of why phonons soften with strain? I am aware of the Grüneisen parameter but it just tells us there is a negative sign.
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25 views

Maximum Phonon Frequency

If I am given the maximum Phonon energy in a monotonic lattice, how would i go about finding the max frequency ? Would this be taking the max energy and dividing by h-bar to give the max frequency ? ...
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What could be the anharmonicity effect if phonon interact with a tilted interface?

If Phonon propagates through c-axis grown structure and at the end reach a tilted interface of GaN, what phenomena will appear there? How anharmonicity is going to effect the phonon propagation ...
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What could be the effect of solid-air interface shape change (square, oval, triangular etc) on phonon propagation at nanoscale range?

I am trying to figure out the solid-air interfacial transmittance of phonon for different shaped interface. Huge acoustic impedance mismatch between solid and air is the challenge to do so. Now I want ...
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27 views

Do tensor product tables for irreducible representations apply for non-symmorphic space groups?

I'm reading Dresselhaus's book on group theory for solid-state physics, but I'm having trouble understanding how to get irreducible representations for phonons away from $\mathbf{k} = \mathbf{0}$ for ...
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40 views

Classical string as a limit case of elastic quantum states superposition

The usuall way to "half-popularly" show that the quantum mechanics formalism is not unconnected to the classical mechanics is to demonstrate a classical case as a limit of a quantum case. The main ...
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190 views

A naive question on the “continuously” degenerate ground states of 1d phonons?

In general, the gapless Goldstone mode is related to the "continuously" degenerate ground states. The Mexican hat potential is an example (see the logo of this SE website), where the bottom circle is ...
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87 views

How to deal with coupled fermion boson operators?

I am a beginner in field theory and I have an exercise where I have a product of coupled fermion boson operators? $$ \hat{b_{l} }^{\dagger}\hat{c_{l^{'}} }^{\dagger}\hat{a_{q} }\hat{b_{l} ...