The tag has no wiki summary.

learn more… | top users | synonyms

1
vote
2answers
50 views

Phonon spectrum

I had a question regarding phonon spectrum in condensed matter. Consider a cubic lattice with '$p$' atoms per primitive cell. Consider the lattice plane used for derivation of the phonon spectrum to ...
1
vote
1answer
91 views

How does a sonic black hole (or dumb hole) work?

I came across this term and I heard they used sonic black holes to detect something analogous to hawking radiation, but I have failed to find sources which explain how exactly they work and how they ...
-2
votes
1answer
641 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 ...
3
votes
0answers
127 views

Coupling of matter field with gauge boson and Goldstone boson:

What's the fundamental difference between the way a gauge boson gets coupled to a matter field, preferably a Fermionic field and the way a Goldstone boson gets coupled to the matter field ? In ...
2
votes
0answers
43 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 ...
2
votes
0answers
53 views

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, ...
2
votes
0answers
86 views

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 ...
2
votes
0answers
75 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 ...
2
votes
0answers
52 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 ...
1
vote
0answers
17 views

Monte calro, Non-polar optical phonon scattering?

I have a question on electron and non-polar optical phonon scattering in GaAs. Is it allowed to consider intravally electron non-polar optical phonon scattering in L-valley of GaAs ?. I found in the ...
1
vote
0answers
27 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 ...
1
vote
0answers
25 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} - ...
1
vote
0answers
57 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} ...
1
vote
0answers
123 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 ...
1
vote
0answers
78 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 ...
1
vote
0answers
48 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 ...
0
votes
0answers
6 views

Why is forward brillouin scattering difficult to observe?

Generally we talk of only the backward Brillouin scattering. And I just know forward scattering is difficult to observe? Why is it so? Does it have something to do with phonon life time? Is it ...
0
votes
0answers
17 views

What is the difference between finite displacement and linear response for calculating vibrational properties?

I see these concepts appearing in the context of calculating phonons and other vibrational properties, but I can't find a concrete explanation of the differences between linear response (DFPT) and the ...
0
votes
0answers
16 views

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!
0
votes
0answers
126 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 ...
0
votes
0answers
37 views

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

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