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.

Filter by
Sorted by
Tagged with
2 votes
0 answers
33 views

Para- and ortho-excitons in solids with spin-orbit coupling

The names para- and ortho-exciton stem from the fact that -- in superficial analogy to para- and ortho-hydrogen -- the wave function that forms the electron-hole bound state can either be a singlet ...
user avatar
  • 496
4 votes
1 answer
69 views

Exciton nomenclature

In many publications on electronic excitations I stumbled across a categorisation of excitons (electron-hole quasi-particles), namely A- and B-excitons. Could someone please explain the difference ...
user avatar
  • 496
7 votes
1 answer
89 views

Can Fermi liquid be obtained by a canonical transformation?

The basic assumption of the Ferm-liquid theory is the one-to-one correspondence between the states of an interacting Fermi gas to those of a gas of non-interacting quasiparticles. The question is ...
user avatar
  • 37.4k
0 votes
0 answers
18 views

Can "bare" TO phonons in polar materials exist by themselves, or are they always phonon-polaritons?

We know that transverse optical (TO) phonons in polar crystals couple to light strongly and can form hybrid light-matter quasi-particles called phonon-polaritons (solid lines in the figure below). My ...
user avatar
0 votes
0 answers
37 views

How do I maximize the overlap?

I am tasked to find the extend to which the many-body eigenstates can be described by adding a single electron or hole to the ground state. or if there exists a single particle orbital $\phi_i$ such ...
user avatar
  • 1
1 vote
0 answers
19 views

Bimolecular recombination: How can it be non-radiative for $e$-$p$ pair?

I have understood that the bimolecular recombination of electrons and holes can be radiative when they meet each other, However, I also heard that there are defect sites that can accept electrons and ...
user avatar
0 votes
0 answers
29 views

Is it possible for a polaron to have a lifetime longer than 1 microsecond?

I am collecting data about the lifetime of a polaron, I just found a paper Probing Nonequilibrium Dynamics of Photoexcited Polarons on a Metal-Oxide Surface with Atomic Precision from PRL, this paper ...
user avatar
  • 575
0 votes
0 answers
35 views

Energy of Quasi-particles in a BCS superconductor

In BCS theory, we are given the energy of the quasi-particles as $E = \sqrt{\varepsilon^2 + \Delta^2}$ in which $\varepsilon = \frac{\hbar^2k^2}{2m} - \mu$, with $\mu$ being the chemical potential. As ...
user avatar
1 vote
0 answers
74 views

Zero of energy and chemical potential in a superconductor

I am having trouble grasping some concepts related to how energy is measured in a superconductor. In BCS theory, we are given the energy of the quasi-particles as $E = \sqrt{\varepsilon^2 + \Delta^2}$ ...
user avatar
5 votes
1 answer
173 views

Excitation spectrum in BCS theory and mean field theory

I've recently been learning about the BCS theory of superconductivity. An extremely rough idea is as follows: given the interacting BCS Hamiltonian $$ H = \sum_{\vec{k}\sigma} \xi_{\vec{k}} c^{\dagger}...
user avatar
  • 1,814
3 votes
0 answers
35 views

Quasiparticle interference experiment - why backscattering is usually dominant?

I am reading Avraham et. al (2018) Quasiparticle Interference Studies of Quantum Materials about quasi-particle interference (QPI) experiments. In the simplest case where they use QPI to study the ...
user avatar
  • 691
3 votes
0 answers
44 views

What's a typical lifetime for excitons, or biexcitons?

I've read that a typical lifetime for excitons in a semiconductor is 1-10 picoseconds. I believe these are Wannier-Mott excitons. What are typical lifetimes of other kinds of excitons, for example in ...
user avatar
  • 518
1 vote
0 answers
46 views

Does zero chemical potential implies zero lowest energy level for non-interacting quasiparticle excitations?

Many of the quasiparticle excitations in solids have non-conservative particle numbers. Examples are phonons, magnons, excitons etc. Therefore, as many posts put, the chemical potential should be zero....
user avatar
2 votes
0 answers
24 views

What is a 'multi-energy band' superconductor?

From Phys.org: They write that in lab experiments they've found a short-lived "Higgs mode" within iron-based, high-temperature (but still very cold), multi-energy band, unconventional ...
user avatar
  • 3,443
2 votes
2 answers
1k views

What is quasineutral in plasma physics?

What is quasineutral gas? In plasma physics, what exactly quasineutral means? In definition of plasma, it is written that plasma is a quasineutral gas of charged and neutral particles which exhibit ...
user avatar
  • 57
6 votes
1 answer
397 views

What would be a simplified explanation of Quasiparticles? [duplicate]

I recently came across a concept in quantum physics called Quasiparticles. They seemed interesting so, I did a little bit of research about them. However, I still don't understand what they are. The ...
user avatar
2 votes
2 answers
369 views

What does having an imaginary part of potential imply? [duplicate]

In DJ Griffiths' ''Introduction to Quantum Mechanics" to describe an unstable particle that spontaneously disintegrates he assumed an imaginary part in the potential. What does that signify? What ...
user avatar
0 votes
1 answer
203 views

The band structure of Weyl Semimetals

Weyl semimetals are topological quantum materials whose low energy excitations emerges as massles Weyl Fermions. They have a band touching point near the Fermi level called Weyl node. What is ...
user avatar
  • 1,187
8 votes
1 answer
337 views

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 ...
user avatar
12 votes
2 answers
331 views

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}\...
user avatar
  • 1,515
2 votes
0 answers
18 views

Lifetime of quasiparticles and poles of the propagator

Suppose I have a system that is invariant under both space and time translations. The Lehmann representation of the propagator says that the poles of the propagator are the exact eigenenergies of the ...
user avatar
  • 307
1 vote
1 answer
142 views

Is a quasiparticle just an eigenstate of the Hamiltonian?

The description of quasiparticles seems to come in two flavors: Completely qualitatively, where it is simply said that different (quasi-)particles interact to "form" a quasiparticle, or ...
user avatar
1 vote
1 answer
58 views

Spin of quasiparticle formed by photon in glass

This previous question about the effective mass of a photon traveling through glass has a few answers that say we can think of it as a quasiparticle with an effective mass. Photons are spin-1, but ...
user avatar
2 votes
3 answers
170 views

Electrons and holes vs. Electrons and positrons

Drawing parallels between electrons and holes in semiconductors, and electrons and positrons in Dirac equation is certainly useful in the context of learning/teaching the quantum field theory methods, ...
user avatar
  • 37.4k
0 votes
0 answers
58 views

What are Skyrmion bubbles?

what exactly is the difference between a skyrmion and a skyrmion bubble? Thanks.
user avatar
1 vote
0 answers
135 views

Intuition and physical meaning of Crystal Momentum and Effective mass of quasi-particles in Solids

I have read various questions related to mine on StackExchange and articles on Wikipedia and some other sources but I still can't get an intuition for the quantities "Crystal Momentum" and "Effective ...
user avatar
1 vote
1 answer
149 views

Neutrinos, quasiparticles and Majorana fermions

In connection with topological quantum computing I encountered term Majorana fermions. According to Wikipedia these are: A Majorana fermion, also referred to as a Majorana particle, is a fermion ...
user avatar
1 vote
1 answer
156 views

Are phonons accepted particles by mainstream physicists?

I just encountered the wikipedia article on phonons, which says that these quasiparticles represent vibrations through matter. Wikipedia says that Phonons have negative mass and negative gravity. But ...
user avatar
  • 476
1 vote
0 answers
71 views

Where can I learn about a history of holes?

Holes are quasiparticles that were historically brought to explain semiconductor physics with extra benefit of simplifying the counting of electrons.Who gave the first idea and how did it develop ...
1 vote
0 answers
52 views

Is the Andreev-Bashkin effect a beyond-mean-field effect?

I am reading about the Andreev-Bashkin effect, which concerns the current drag from the interaction between two superfluids. Basically, the interaction between two coupled superfluids leads to the ...
user avatar
1 vote
0 answers
58 views

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 ...
user avatar
  • 1,618
2 votes
1 answer
249 views

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 ...
user avatar
  • 407
14 votes
2 answers
786 views

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 ...
user avatar
1 vote
0 answers
36 views

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 ...
user avatar
1 vote
1 answer
174 views

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 ...
user avatar
  • 69
0 votes
1 answer
62 views

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?
user avatar
1 vote
0 answers
50 views

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 ...
user avatar
6 votes
1 answer
1k views

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 ...
user avatar
1 vote
1 answer
120 views

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 ...
user avatar
  • 392
1 vote
0 answers
28 views

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 ...
user avatar
  • 26.3k
3 votes
0 answers
218 views

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 ...
user avatar
1 vote
1 answer
1k 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.
user avatar
  • 93
2 votes
2 answers
300 views

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 (...
user avatar
2 votes
1 answer
2k views

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 ...
user avatar
5 votes
1 answer
857 views

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 ...
user avatar
  • 1,034
1 vote
1 answer
368 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?
user avatar
  • 24k
2 votes
1 answer
93 views

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 ...
user avatar
6 votes
2 answers
1k views

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^\...
user avatar
  • 69
3 votes
1 answer
189 views

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 $\mathrm{Im}\,\Sigma=0$...
user avatar
0 votes
1 answer
331 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 ...
user avatar
  • 8,454