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19 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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0answers
22 views

How do phonons and spinwaves interact? [closed]

What governs the coupling of acoustic phonons to transverse and longitudinal spinwaves? Is there a simple picture?
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2answers
26 views

Pin point sound wave on phonon dispersion

Imagine a sound wave of 1 Mhz is pushed into a material, in order to plot this on a phonon dispersion relation (E-K plot) - should I convert the 1 Mhz into wavelength(lambda) and find the equivalent ...
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2answers
19 views

what is quasi-particle and its behaviour in solid?

I came across the term on several occasion while reading solid state physics and statistical mechanics. Didn't understand quite well. It'll be help if it's explained.
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0answers
20 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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1answer
58 views

What is a clear definition of vibrons?

What is a clear definition of vibrons? Vibrons are localized Phonons and I need more information about them. It is somewhat vague to me. Can you give some references, please?
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2answers
48 views

Are there materials that strongly (macroscopically) vibrate under light of certain frequencies? If so why?

Picture an imperfect plane of loose particulate matter like sand or silt. Are there materials where if I shine light (not isotropically) on the plane I could get the particles to vibrate with large ...
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1answer
38 views

Difference between mechanical modes and phonons

As stated in this review article: Mechanical modes are long compared to the interatomic spacing. It is natural to make the distinction between nanomechanical modes and phonons: The former are ...
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0answers
37 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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0answers
48 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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1answer
67 views

phonons with next-nearest harmonic interactions

Given an account of the propagation of atomic vibrations along a monatomic chain of atoms, mass $m$, in which the spacing between atoms is $a$ and in which atoms, distance $na$ from each other are ...
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2answers
71 views

What's phonon mean free path

This is probably a naive question but still. Phonons are quasiparticles that emerge when we quantize motion of a lattice. In this sense, they have no location in space, they are just energy quanta of ...
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1answer
74 views

Are acoustic phonon frequencies always linear in k?

I'm confused by a discussion in Ashcroft and Mermin's textbook on pg. 512-513. They say that if we have a bunch of ions in a solid and neglect the effect of the conduction electrons, then waves will ...
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1answer
95 views

How to calcualte density of state from computed phonon dispersion?

I have numerically computed phonon dispersion using small displacement method by solving dynamical matrix along high symmetry direction [100], [110] and [111] for f.c.c lattice. Now I want to ...
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1answer
33 views

How do phonons affect the work function?

How do phonons affect the work function? Could phonons that are directed towards a single atom, such as in a body-centered cubic crystal, increase the amount of thermal excitation and thus decrease ...
2
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1answer
75 views

What is a single-phonon?

From what I understood from wikipedia, as well as some other resources, each phonon corresponds to a normal mode oscillation, and the creation operator to create a phonon of wavevector $k$ is: $$ ...
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0answers
36 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 ...
2
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1answer
45 views

How does phonon scattering change the distribution function?

For a one-dimensional structure, we know that the modified distribution function has the following energy dependency in equilibrium: \begin{equation} Z(\varepsilon)\,f(\varepsilon) = ...
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2answers
77 views

When do optical phonon branches arise?

As far as I understand from what I'm studying, only when you have more than one kind of atom in the lattice structure, will the phonon have an optical branch, or else it should not have an optical ...
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1answer
47 views

Quantization of energy of phonons

when taking into account of energy of photons, the relationship $E=nh\nu$ stands because it is said that the Energy is proportional to the frequency of the electromagnetic wave, however when the ...
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1answer
37 views

Help with the analytical solution for the dispersion relation of an elastic wave with wave vector k

I was studying Phonons and Lattice vibrations and came across the equation. I want the mathematical solution for this. $$M\frac{d^2u_n}{dt^2}=C[u_{n+1}+u_{n-1}-2u_n]$$ from here it is argued that ...
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2answers
225 views

Has a phonon, a formal quasi-particle, ever been observed as a point particle?

Phonons are a nice tool to simplify the quantum-mechanical description of lattice vibrations by identifying the ladder operator of normal modes as creation operators of a certain quasi-particle. In ...
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1answer
60 views

Phonon modes in one-dimensional monoatomic chain

I am familirazing myself with the lattice dynamics reading Ashkroft-Mermin (p2 ch 22). My question is what it the mathematics behind the deriviation $U^{harm}=1/2 K \sum_{n} [u(na)-u([n+1]a)]^2$ ...
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0answers
48 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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0answers
19 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 ...
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0answers
56 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 ...
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2answers
59 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!
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0answers
63 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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1answer
165 views

What is the relationship between Raman peaks and phonon vibration modes?

I've seen Raman spectra, such as here, where peaks at certain wavenumbers were identified with phonon vibration modes (TO, LO, TA, LA). What is the relationship behind this, and how could I make such ...
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2answers
157 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 ...
2
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1answer
74 views

Why is the number of phonon modes in a solid restricted to a finite value?

Kittel's Thermal Physics (Amazon link) makes the statement: There is no limit to the number of possible electromagnetic modes in a cavity, but the number of elastic modes in a finite solid is ...
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0answers
74 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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0answers
60 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} - ...
2
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2answers
162 views

What's the relationship between sound speed and acoustic phonons?

In the textbook, it says that the slope of the acoustic branch of phonons equals to the sound speed. There are 3 kinds of acoustic phonons including TA and LA phonons. Does it mean that there are also ...
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0answers
97 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, ...
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1answer
86 views

Why does a thermal memory need a thermal bath?

In the article "Thermal Memory: A Storage of Phononic Information Phys. Rev. Lett. 101, 267203 – Published 29 December 2008" it's said that a thermal memory need a thermal bath, similar to a power ...
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0answers
171 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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0answers
105 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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0answers
77 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} ...
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1answer
171 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 ...
0
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1answer
166 views

How to define the heat current in an isotropic continuum material

I'm doing a FDTD (finite difference time domain) simulation of an isotropic continuum material. And I have several questions. How do you define the energy transferred through an isotropic continuum ...
3
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0answers
178 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
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1answer
187 views

Help needed to understand the dispersion curve of a 1D lattice with diatomic basis

I am trying to understand the dispersion curve (as shown below) of a 1D lattice with diatomic basis. Here are my questions: Can both optical and acoustic branch of phonon simultaneously exist in ...
2
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2answers
91 views

Potential Energy in solids: Why are different equations used for deriving lattice constants and for deriving the properties of phonons?

While deriving the equilibrium lattice constants we use expressions for potential like Lennard-Jones potential which have 6th and 12th order terms or Madelung energy for ionic crystals. While ...
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1answer
247 views

Non-trivial solution for a linear set of coefficients involved in the phonon modes of a semiconductor quantum dot

I am trying to use the method outlined in this linked paper (T. Takagahara, Journal of Luminescence, 70 (1996), pp. 129-143) to find the phonon-exciton coupling in a spherical PbS quantum dot. In Eq ...
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3answers
1k views

Can someone explain LO-TO Splitting?

LO-TO splitting occurs in an ionic (i.e. polar) solid such as GaAs or NaCl. What happens is that the degeneracy of the transverse optical (TO) and longitudinal optical (LO) phonons at $k=0$ is broken ...
2
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1answer
125 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 ...
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1answer
94 views

Understanding EM Fields

I am an electronics engineering major and some questions arise when studying communications technology that utilizes wireless technology. In particular, I am more of a complete picture kind of person, ...
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1answer
28 views

Do the characteristic vibrational modes of a material define how much will a material heat up upon radiation excitation?

Do, and if yes how, does the intensity and energy of the Raman modes of a material make it to heat more by radiation excitation. I see phonons and vibrations of the lattice as heat, but maybe I'm ...
2
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1answer
272 views

Difference between the 'phonons and virtual photons'

I understand what are virtual photons and the difference between the real and virtual photons. However, I am not able to clearly distinguish the difference between the 'phonons and virtual photons'. ...