Phonon Definition and 92 Threads

If I understand correctly, when an electron drops to a lower energy state and emits a phoTon, this is a discrete or "atomic" event in the sense that it can't be meaningfully broken down in terms of more detailed sub-processes or interactions. Now in the case of phoNon emission, it is also...

Hello everyone! I'm trying to replicate phonon density of states (PHDOS) diagrams for some solids using Quantum Espresso. The usual way I do it is the following one: scf calculation at minima (pw.x) Calculation of dynamical matrix in reciprocal space with nq=1 or 2 (ph.x) Calculation of...

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My first question here, so maybe not adequate or in the wrong topic, excuse me. I try to understand vibrating light harvesting antenna in biochemistry but it is a question of physics. We talk about a molecule with an emission spectra peak of about 650 nm. In classical physics electrostatic and...

In the following pdf I tried to calculate the density of states of free electrons and phonons. First, I found the free electron DOS in 1D, it turns to be proportional to (energy)^(-1/2) and in 2D it is constant. However, I am not sure I found the DOS for phonons in the second part of the...

If you go beyond the harmonic approximation, phonons can not be thought as independent quasiparticles anymore and phonon-phonon interactions are taken into account. This eventually translates into the fact that phonons frequencies get renormalized ( ##\omega \rightarrow \omega^′ +i\nu ##)...

I found the mean to be $$\langle n\rangle=\vert\alpha\vert^2 \tanh(\alpha^2)$ and $\langle n^2\rangle=\vert\alpha\vert^2 \left( \alpha^2\sech(\alpha^2)^2 + \tanh(\alpha^2) \right)$$. Do you know if there is any reference where I can check if this is correct?

Suppose I prepare an experiment where I excite a single mode of oscillation of the lattice, that is something like ##u(x, t) = Ae^{i(kx-\omega t)} ## (in the classical limit). The energy corresponding to that mode should be ##E = \frac 1 2 \rho L^3 A^2 \omega^2 ##. If I equate this equation to...

Hi, I have a question regarding Phonons and daily experience: Let's say I have a table and I hit it, does it mean Phonons were created where I've hit on the table? Meaning: By hitting the table, I'm giving energy to it, this energy goes to the motion of the table atoms, and this motion of the...

In most standard exposition of (the mean-field theory of) charge density wave (CDW), phase and amplitude fluctuations are introduced as the collective excitations. Kohn anomaly in the acoustic phonon dispersion is also mentioned as temperature goes from the above till the CDW transition...

Hello everyone, I need some confirmation on something: As far as I understood, the raman spectroscopy measures the inelastic scattering of a photon in a medium through the absorption or the emission of a phonon in the medium. The energy and the momentum is conserved...

What is the sign of phonon mass? A substance of uniform composition, in a field of gravity, has pressure increasing downwards. This causes the compressibility to decrease downwards - and speed of sound to increase downwards. In a gradient of downwards increasing velocity, a wave propagating...

Phonons on their own lead to the common heat equation. One sees that for example in insulators or non doped semiconductors. However in metals (or conductors), the electrons are the ones that are mostly responsible for the heat transfer, which extremely surprisingly to me, is also of the form of...

Mossbauer spectroscopy is an example of a nuclear (de)excitation coupling to a lattice phonons Are there any other examples of this phenomena ?

Hi, I'm looking into how phonon dispersion changes with pressure analytically and need to know how the atomic spacing in copper changes with pressure in order to model the crystal. I can't find any helpful papers online :( Any help would be appreciated thanks e

I saw this paper that talks about phonon sidebands, multiphonon relaxation, and phonon-assisted energy transfer. I was skimming through each of the equations, but I have problem understanding the formulation of some of them, for example Equation (3.17): g_{\pm }(t) = \int d\omega...

Dear all, I am not understanding well the "phonon-assisted" energy transfer between lanthanide ions and I need some clarifications. There is a theoretical work by Miyakawa and Dexter (doi:10.1143/JPSJ.32.1577) which explains how phonon plays a role in transferring energy from one (4f-state of)...

Homework Statement Hi guys, I'm currently writing an extended essay in Physics looking at the effect of percentage composition of Sn has on the electrical resistivity of SnPb Solder. I've noticed that Sn is listed as being a better conductor than Pb, despite trends of periodicity and have been...

Is it possible to detect a single phonon? If yes, can it be detected at a well-defined position?

i work on phononic crystals and i want to find solids with diffrent sound velocities and mass density in diffrent temprature i can just find BST but i need more matherials please help me my friends best regards

When we say that a phonon vibration mode has an average energy <E> are we saying that all atoms (or harmonic oscillators) in a piece of matter (eg. a nanoparticle) will also has that energy, or that the piece of matter as a whole will have that energy ? In the second case the amplitude of the...

Does phonon required a minimum energy in the absorption process of an indirect band gap, and why?

As far as I understand, phonons are just thermal vibrations of atoms in a lattice and blackbody radiation is just the radiation emittied due to thermal oscillations accelerating the atoms back and forth. Is there any example of a derivation of the Planck equation from considering black body...

So I see them in the books labelled as accoustic and optical phonons but I don't seem to find a comprehensive treatment of the matter for a beginner who doesn't know a thing about the dispersion curves. I'd prefer not to dwell too much into the mechanical treatment if possible since I just need...

klotza submitted a new PF Insights post The Interaction of Sound and Light Continue reading the Original PF Insights Post.

Hello friends. My question consists two parts, 1-What is the difference between an optical and an acoustic phonon? 1-What are the conditions by which we can decide the type of phonon i.e optical or acoustic phonon ? Hope to get the reply soon.

Hello, I am new to the forum, so I am directly stating my questions. 1)What determines the density of states of Phonons in a semiconductor? 2)Does degeneracy of semiconductors depend only on doping? Thanks

It is said phonon(not photon) in superfluid experiments could also produce similar upper-limit speed effect which I'm not sure if that's also Lorentz invariant. Another problem is that I can't dig out those paper that demonstrates this kind of effect. Anyone ever seen any of this paper? Thanks..

Consider a monoatomic 1-D chain of atoms (only acoustic branch). What happens with the inference of the dispersion curve through neutron scattering? In one dimension, conservation of momentum dictates $$ k'=k+K_s $$, if k_s is the phonon momentum vector and we only consider processes where a...

I am reading Frohlic's paper on electron-phonon interaction. Frohlic.http://rspa.royalsocietypublishing.org/content/royprsa/215/1122/291.full.pdf Here author has introduced the quantization for complex B field in this paper and claimed to have arrived at the diagonalized form of the...

I am aware that phonons are lattice vibrations - and that the amplitude of vibration would depend on the temperature. But say, at room temperature what would the order of magnitude of these lattice vibrations be ? In particular, in continuum limit these phonons can be treated as elastic...

Hey all, I am trying to recreate the phonon dispersion plot of the paper below http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-730-physics-for-solid-state-applications-spring-2003/projects/ProjP21.pdf The problem is I do not know what the Tau, L, and X on the x-axis...

hello every one , I want to know how we get phonon frequency spectrum theoretically by using three modes and dispersion relation, can anyone explain it. for example it is phonon energy correspond to density of state how it is obtain?

Double stranded DNA are bind with hydrogen bonds in between the nitrogenous bases, Usually we use high temperature for denature,so can we break the hydrogen bonds with phonon because shorter wavelength give rise to heat, weather it is possible to denature the DNA?

Hi! How exactly is the relationship between number of atoms in the basis of a bravais lattice, and the number of possible phonon modes? So, for example, if you have 2 atoms in a basis you get 3 acoustical and 3 optical modes in 3 Dimensions. But why exactly is this? Do you need to set up the...

Aluminium has an fcc structure, which is a simple cubic lattice with four Al-atoms in the basis. On the other hand, diamond has a diamond structure, which is a simple cubic lattice with 8 atoms in basis. Now, diamond has optical modes in addition to acoustical, while Aluminium does not. What...

I was hoping someone could tell me the phonon frequency of the electrons for YBCO with hole doping of about .2 and a critical temperature of around 75-70°K at about 70°K. An answer in Hz would be preferred, or failing that, in cm-1 with the wave speed. Also, might the Kohn anomaly influence the...

I was doing some calculations earlier and tried the ratio between a metal's fermi temperature ##T_F## and debye temperature ##\theta_D##: \frac{T_F}{\theta_D} = (6 \pi^2)^{\frac{1}{3}} \left( \frac{\lambda}{a} \right) where ##\lambda = \frac{\hbar}{2 m_e c}## and lattice spacing is ##a##. I...

... electron transport. 1. Homework Statement Electron - Phonon scattering, derive the contribution to electron transport. Homework Equations Trig. The Attempt at a Solution Am I being REALLY stupid here, I can't see how the equation matches the triangle. If you resolve KF' doesn't KF'...

Homework Statement Homework EquationsThe Attempt at a Solution Since it's 3D, I assume there's at least 3 acoustic modes and 3 optical modes? After all, the soundwaves/phonons must be able to travel in all directions. Further on, I know both longitudinal and transverse modes are possible...

Hi all, In Charles Kittel (Introduction to Solid State Physics) He writes : U (Total Phonon Energy ) = Σk∑p((ħ*ωk,p)/((exp(ħ*ωk,p/τ))-1)) I understand this, but then he integrate over k and multiply by density of states : U (Total Phonon Energy ) = ∑p∫dω*Dp(ω)*((ħ*ωk,p)/((exp(ħ*ωk,p/τ))-1))...

I am interested in how phonon softening would lead to changes in a crystals elastic properties but I don't understand what actually is the consequence of this. What would be affected by a reduction in energy to phonons in a crystal? My best guess would be a reduction in energy to phonons causes...

I'm having trouble simplyfying this, I guess there's a trick but for the life of me can't remember what it is. Here is what I have so far: ##\omega ^{2} = f\left ( \frac{1}{m}+\frac{1}{M} \right )-f(( \frac{1}{m}+\frac{1}{M} \right ))^{2} - \frac{4q^{2} a^{2}}{mM})^{\frac{1}{2}}## so I divide...

Hi there, I have a problem on phonon perturbation's effect on diffraction pattern. Assume atomic planes parallel to (100) of bcc lattice is periodically perturbed by phonon. How will diffraction pattern be modified as a result of such perturbation? Will we see any diffraction peaks in addition...

The low temperature heat capacity was experimentally shown to go as T^3 for low temeperatures (and as T for even lower temperatures for metals). This result came out of Debye's model after he modified Einstein's model, relaxing some of his assumptions. I have a few questions on Debye's model...

Good day everyone. I would like to know about the lower limit of the frequency range of active acoustic phonon modes. Textbooks say it can reach zero. But I am curious about whether it can be very small, such as 1 micro volt or the like. Would a phonon mode of so small energy be of any...

I am conducting an experiment on the parabolic trough that concentrates the solar light and heats up water. I am using different metal sheets (zinc, aluminium, copper, tin...) for the parabolic trough to see the differences in temperature change. I researched on a few things and I understand...

In a metal, can one electron decay into one lower-energy electron plus one phonon? (i.e., can the attached Feynman diagram occur?) If we replace phonons by photons and consider the process in a vacuum, I guess this is prohibited because you can always boost to a frame where the incoming and...

Phonons are quantized lattice vibrations. They are traveling waves of the form exp(ikr) taken to satisfy periodic boundary conditions. I'm guessing periodic boundary conditions are equivalent to demanding the waves to be zero at the boundary. which is what characterizes standing waves (right...

This occur when two phonons interact and the sum of their momenta add to a new wavevector outside the new Brillioun zone. The resulting wavevector is then mapped back into the Brillioun zone by subtraction of a suitable reciprocal lattice vector. I don't think I understand the physics in all of...