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.
Questions tagged [quasiparticles]
135 questions
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votes
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Are W & Z bosons virtual or not?
W and Z bosons are observed/discovered. But as force carrying bosons they should be virtual particles, unobservable? And also they require to have mass, but if they are virtual they may be off-shell, so are they virtual or not.
user1702
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votes
5 answers
What is a phonon?
I am trying to understand intuitively what a phonon is, but for the moment I find it quite difficult (having a limited background in quantum mechanics, an undergraduate course in non-relativistic QM). In fact, I find it hard to formulate good…
doetoe
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7 answers
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 heavier unstable particles are just transient…
Justin
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4 answers
Are elementary particles actually more elementary than quasiparticles?
Quarks and leptons are considered elementary particles, while phonons, holes, and solitons are quasiparticles.
In light of emergent phenomena, such as fractionally charged particles in fractional quantum Hall effect and spinon and chargon in…
leongz
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3 answers
Quantum mechanics - how can the energy be complex?
In section 134 of Vol. 3 (Quantum Mechanics), Landau and Lifshitz make the energy complex in order to describe a particle that can decay:
$$
E = E_0 - \frac{1}{2}i \Gamma.
$$
The propagator $U(t) = \exp(-i H t)$ then makes the wavefunction die…
user22037
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How to get an imaginary self energy?
The Lehman representation of the frequency-dependent single particle Green's function is
$$G(k,\omega) = \sum_n \frac{|c_k|^2}{\omega - E_n + i\eta}$$
where $n$ enumerates all the eigenstates of the system, $c_k$ is the overlap between…
Lagerbaer
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Phonon carries zero spin. Why?
photons and phonons both have polarization, we attribute spin 1 for photons but spin 0 for phonons. Why?
richard
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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 are
new excitations that appear when there are…
João Bravo
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17
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3 answers
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 differ, however I don't know in what sense. Can…
Jan Hirschner
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What is the concept of hole in semiconductor physics?
What is a hole? And how should we describe it to study it properly?
Many textbooks refer to it as an empty state that carries a positive charge, but how can an empty state carry a positive charge? And other textbooks refer to it an physical particle…
Abdelrahman_200
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Spectral function and bound states in condensed matter
In condensed matter physics (like in QFT) we can use Feynman's diagrams to compute the self-energy. From here we can obtain the spectral function as:
$$
A_{\mathbf k} (\omega) = \frac{-\frac{1}{\pi}\mathrm{Im}\Sigma_{\mathbf…
RedGiant
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votes
5 answers
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 possible for electron-electron interactions to…
ChickenGod
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3 answers
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 fermions. But as I understand, the spin in graphene…
Ruslan
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Can anyons emerge from momentum-space other than spatial dimensions?
So far in condensed matter physics, I only know anyons(abelian or nonabelian) can emerge as quasiparticles in 2D real-space.
But is there any possibility to construct anyons in momentum-space ? And what about the braiding, fusion rules in …
Kai Li
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Is differentiating particle and quasiparticle meaningless?
The common notion for quasiparticle is that it is only a toolkit to tend emergent phenomena in solid-state physics easily, and it is a different thing from a "real" particle. But what I still doubt about is that I still don't know what "demarcates"…
윤종인
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