Questions tagged [quasiparticles]

Quasiparticles and Collective Excitations are emergent phenomena that occur when microscopically complicated systems such as solids behave as if they contained different weakly interacting particles in free space. Examples are: electron quasiparticle, hole, exciton, phonon, polariton, magnon, plasmon, polaron.

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A mathematical definition of quasi-particle based on second quantization

Is there a mathematical definition of a quasi-particle? So far, from what I see in textbooks, a quasi-particle is that created by the creation operator $d^*$ which was obtained by a Bogoliubov ...
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Why do we have to introduce quasiparticles in the Fermi liquid theory

Why is it necessary in Fermi liquid theory to introduce quasiparticles? I understand the notion of system where someone can turn on the interactions slowly (i.e., adiabatically), but I do not ...
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Are there Goldstone bosons in 1D or 2D?

The Mermin-Wagner theorem states that continuous symmetries cannot be spontaneously broken at finite temperature in systems with short-range interactions in dimensions d ≤ 2. And Goldstone bosons ...
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What is the definition of a bipolaron and a dipolaron?

I wondered about the exact definition of a bipolaron? In particular, if I have an oxygen vacancy in a metal oxide and the 2 excess electrons (when forming a neutral oxygen vacancy) localise on the 2 ...
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What are dark excitons and how to find them?

I am reading about excitons and I encountered a few times the term "dark exciton" but I have a hard time finding a good definition. I tried to google it but I only find scientific articles where the ...
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Statistics of a quasiparticle

I was trying to understand the Chern-Simons theory description of the fractional quantum Hall effect. I was trying to follow this article. After integrating out Lagrangian the mutual statistics of two ...
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What creates a negative charge in the material?

What creates a negative charge in the material? Is it an electron or a holon? Holons as I understand is a math. But what then creates an electrostatic repulsion? Is it still electron?
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Massless Dirac fermions vs helical Dirac fermions

Some papers when, dealing with graphene, write about charge carriers called helical Dirac fermions that have a conical energy–dispersion relation and a conserved quantity $\sigma\cdot k$ (pseudospin–...
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Is there a quasi-particle corresponding to sound wave in air medium? [duplicate]

I have seen many quasi-particle here in this list. Is there any quasi-particle concept for sound wave in air medium? If it exists, what's the purpose and usefulness of it? If it does not exist, is ...
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How do electron holes have spin, and how do they interact with “real” particles / vice versa?

So, I thought I had an uneasy truce with quantum mechanics but I read something today which made spotted combat flare up in my mind again. In solid state semiconductor free electrons certainly have ...
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Microscopic and macroscopic description of spin waves

Hamiltonian Consider the one-dimensional Heisenberg ferromagnet specified by the Hamiltonian $$H = -\frac{|J|}{2}\sum_{i,\delta} \mathbf{S}_i\cdot \mathbf{S}_{i+\delta}.$$ Here $i$ labels the spin ...
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Can we track phonon's path similarly to how we track electron's path in a bubble chamber?

An answer to a recent question argues that Standard Model's particles like electron are "real" because we can see their tracks in e.g. bubble chamber. So now I wonder: can we track quasiparticles ...
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What determines if a quasiparticle is a spinon or a vison?

Across topological literature, I've seen references to spinons and visons. In Kitaev's famous "Anyons in an exactly solved model" paper, he mentions that visons are "spinless bosons" whereas spinons ...
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343 views

What is Quasi-particle weight? [closed]

Hi I just heard this phrase from my classmate yesterday, I am wondering whether someone can explain this real quick for me.
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In what sense are quasiholes and quasiparticles “excitations” in Fractional Quantum Hall (FQH) systems?

In the theory of Fractional Quantum Hall states, one often sees quasi-holes and quasi-electrons (or quasi-particles) being called "excitations" from the ground state initially given by Laughlin (...
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Why does a phonon obey the Bose statistic?

Could somebody please explain why the phonon must be a Boson (strictly speaking, it must obey the Bose statistic) regardless what it is composed of? (As I have heard, the lattice vibration of both ...
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Quasiparticle density of states : how to give it a meaning as the quasi particle are interacting?

There is something I don't understand about quasiparticles density of states. I work with the book "Introduction to many body physics" from Coleman. When he introduces the quasiparticle he does the ...
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177 views

Can magnons or phonons exist at zero temperature?

Can in principle, magnons or phonons exist at zero temperature? If not, why? If yes, how?
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What is the order of magnitude of the energy released in Majorana fermions collision/annihilation?

Majorana fermion experiment It has been observed a quantum state in a one atom thick wire which in a certain energy range behaves like a Majorana fermion. It is a quasiparticle that arises out of the ...
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Why must the Bogoliubov transform preserve anticommutation relations?

$\mathbf{Background}$: In my research I am studying the Ising model, expressed in terms of Jordan-Wigner fermions: $$ H = \sum_{j=1}^n(c_j - c_j^\dagger)(c_{j+1} + c_{j+1}^\dagger) + \lambda c_jc_j^\...
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Why quasiparticles do not decay in finite system in random phase approximation?

I have tried to apply the conventional recipe of calculating electron self-energy part $\Sigma$ in the random phase approximation (RPA) to the case of finite system and obtained $\mathrm{Im}\,\Sigma=0$...
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234 views

Is it possible to create a photon with energy lower than the plasma frequency inside a plasma?

Suppose we have a plasma with corresponding plasma frequency $\omega_{\text{pl}}$. Next, assume that there is some scattering inside the plasma, due to which photons can be created. Is it possible to ...
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Example of spin chains with finite-lifetime quasi-particles?

Does anyone know a one-dimensional spin model where the low-energy excitations have a finite lifetime? (E.g. in terms of the spectral function $\mathcal S(k, \omega)$ this means one would get a finite ...
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How to unify these two distinct pictures of spin waves?

For convenience let's focus on an isotropic ferromagnet, $H = -\sum \boldsymbol{S_i \cdot S_j}$. On a classical level we are often given the picture of spin waves as slowly rotating spins, each ...
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Physical interpretation of a complex potential for a particle in quantum mechanics

In Griffiths' Quantum Mechanics, it is mentioned in a problem that For an unstable particle that spontaneously disintegrates with a lifetime $\tau$, the total probability of finding the particle ...
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Why are excitons not found in metals?

In this Wikipedia link, the definition of exciton is given by An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. ...
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Collective excitations: localized or delocalized?

When condensed matter physicists talk about collective excitations in a crystal such as phonons, magnons etc, do they picture these excitations as necessarily delocalized in the crystal? If they do ...
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Charge balance and Bogoliubov quasiparticles

Before trying to understand charge imbalance in superconductors (eg Hübler et al., Phys. Rev. B 81, 184524, Quay et al., Nature Physics 9,84–88 (2013)) I thought I had better check I understand the ...
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What is invalidated when turning on many body interactions in a crystal?

I have just started to think about strongly interacting particles and Fermi liquid theory, and I have two questions. For non interacting particles moving in an potential field, we know that the ...
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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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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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Derivation of Aharonov Bohm effect for Quasiparticles

I've noticed the following: Observation: Central results in the condensed matter physics rely on Aharonov Bohm-type arguments involving quasiparticles with fractional charge. However, I can't see ...
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Fermi Golden Rule derivation of quasi-electron lifetime

I wonder if there is a detailed derivation of the quasi-electron lifetime: \begin{equation} \frac{1}{\tau_k}=\frac{2\pi}{\hbar}\frac{1}{V^2}\sum_{k', q}\sum_{\sigma}|V_q|^2f_{k'}(1-f_{k-q})(1-f_{k'+q}...
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Which quasiparticles follow which statistics [closed]

Let me say beforehand that I know this is an ill-defined question, but I believe it is useful anyway. For these common quasiparticles: Phonons Holes Plasmons Excitons Plasmon-polaritons What ...
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How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles?

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles? It would appear to a layman such as myself that these ...
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Bimolecular recombination in few words

I'm making a short seminar about VERY broad topic of fullerenes in photovoltaics, but I'd like it to be educational (not just full of words hard to audience to make them think I'm smart). In one of ...
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What is the difference between a magnon and a spinon?

For a long time, I thought the terms "magnon" and "spinon" were equivalent, describing the collective spin excitation in a system. Lately, I have seen remarks in the literature that they indeed do ...
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Can spin-1/2 emerge as a property of quasiparticles if original description of the system was without spin?

When we consider a band structure of some crystal, we can get a model of particle-antiparticle system like electrons and holes. In graphene, for instance, we even get a model of massless Dirac ...
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How do electrons get a charge?

Electrons belong to a group of elementary particles called leptons. There are charged and neutral leptons. And electron is the charged one. But how come it got charged? The negative or positive ...
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Exciton in semi-conductor

I don't understand why an exciton describes only the interaction between an electron hole and an electron in the conduction band? How is this interaction different from the interaction between an ...
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Rigorous distinction between quasiparticles and collective excitations

I would like to hear your opinion on the question whether there is an accepted distinction between both concepts in condensed matter physics. I would tend to use the word quasiparticle for dressed ...
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Is it possible for quasiparticles to form charge density wave of quasiparticles?

What if the quasiparticle has fractional charge? -----UPDATE------ For example, 1d kink has e/2 charge, if view kink like electrons in 1d (we know there is 1d charge density wave of electrons), is ...
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Excitons in metals-do they exist?

Recently I red an article "Surface Enhanced Fluorescence". It is a topical review by Emmanuel Fort and Samuel Gresillon. Here it is: http://turroserver.chem.columbia.edu/surfaceplasmons/pdf/...
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Naive questions on Goldstone modes and a possible duality relation?

For example, let's consider a 1D spin-1/2 ferromagnetic (FM) Heisenberg chain $H=-J\sum_{i=1}^{N}\mathbf{S}_i\cdot\mathbf{S}_{i+1}$ with periodic boundary conditions. Now we want to study its low ...
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What is the first excited state of the honeycomb Kitaev model in its gapped phase?

As we know, there are both gapless and gapped phases of the Kitaev model, and let's fix the couplings $J_x,J_y,J_z$ such that the model being in the gapped phase. My question is, what is the first ...
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Does electron-electron scattering contribute to resistivity?

Electron-phonon and electron-defect scattering clearly contributes to resistance, but pure electron-electron scattering conserves the total momentum (and energy) of all the electrons. Then, how is it ...
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Derivation of existence of energy band gap in semiconductor (solid State)

I am looking for both a mathematical and a physical reason for energy band gap in metals. For Physical reason, I was told that at each reciprocal lattice, you could have Bragg scattering, that would ...
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quasiparticles resembling monopole energy generator

Is it possible using quasiparticles that superficially resemble monopoles to make a generator providing a sustainable source of power
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Photons and phonons

A few months ago I asked about phonons. I got some very good answers but I still have difficulty getting an intuition for phonons, while somehow photons, which in many ways are similar and which I ...
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Can excitons be understood in terms of classical quantum physics?

From what I understand, an exciton is an electron-hole pair in a semiconductor that exists in a bound state (through the electrostatic potential). I have seen it stated that this pair behaves in a way ...