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Questions tagged [exchange-interaction]

An effective, but not actual, force used for effective description of geometric effects between identical particles, such as the apparent repulsion between fermions due to the Pauli principle.

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DMI as a Superexchange?

Superexchnage interaction is an indirect exchange interaction between two magnetic ions; Anderson proposed a model that says the origin of this type of exchange is due to the arrangement of Molecular ...
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Ferromagnetism vs antiferromagnetism

In ferromagnetism the spins align in the same direction, but in antiferromagnetism the spins align in the opposite direction. Both are due to the so-called 'exchange interaction', with a negative ...
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What is exactly "spin of atom"? [closed]

$$E_{\text{ex}}=-2 J_{\text{ex}} \mathbf{S}_i \mathbf{S}_j =-2 J \mathbf{S}_i \mathbf{S}_j \text{cos}\phi$$ I'm studying magnetism and often see sentences like "spin $i$ product spin $j$" ...
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Is electron capture the exchange of a virtual $W$-boson?

Betaplus: an upquark emits a $W^+$-boson which turns it into a downquark and then decays into a positron and electron neutrino. Electron capture: an upquark emits a $W^+$-boson which is absorbed by a ...
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Calculating the Second Virial Coefficient

I have seen many different derivations of the second virial coefficient, but none of them explains how they turn a double integral into a single integral. The second virial coefficient is: $$ B_2=-\...
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Determining force of interaction from a decay equation

I have the decay equation $$p + π^− → n + K^− + π^+.$$ I have been told the force of interaction in this is the weak nuclear force, but I was looking for an explanation of how you can work that out ...
Techwizard's user avatar
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Can exchange interaction exist between electron and muon? [closed]

I'm studying about the exchange interaction and it's quite confusing. Why does it happens between same kinds of particle? How about electron and muon? Or one particle and another one which has all the ...
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Exchange interaction between neutral particles

I imagine the following thought experiment: Let us prepare two identical neutral fermions with identical spin and antisymmetric spatial wave function in one spatial dimension. Let the initial state be ...
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Is exchange interaction just a consequence of approimations?

My background is in molecular physics, and I have encountered the term 'exchange interaction' in this context first, but it seems to be used in many areas of physics. In my understanding, seems to be ...
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Discussion on exchange energy

When we ionize hydrogen (no exchange energy in hydrogen) by supplying energy to it, electron use it to break the attraction between the nucleus and itself and comes out of the reach of the nucleus. ...
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How do spins interact with each other?

When talking about magnetism and the interaction of spins, the most basic model seems to be the Heisenberg model with an interaction of the form $ -J \vec{S}_1\cdot \vec{S}_2$. The origin of the ...
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How do I deal with linear terms in an ferromagnetic exchange interaction Hamiltonian?

I am currently working on deriving the dispersion relation of spin waves in a ferromagnetic monolayer, using the Holstein-Primakoff formalism. Regardless of the specifics, in my derivation I am ...
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Significance of Self-Interaction in Hartree Potential

According to DFT (and correct me if I'm incorrect) the terms of Hartree potential and exchange correlation potential are introduced to simulate the particle (fermion-fermion) interaction in our system ...
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I'm trying to solve the expression for Dirac exchange, but I'm not understanding the variables change employed. How can I perform it? [closed]

I'm trying to perform the variables change employed in the book "Density Functional Theory of Atoms and Molecules", by Parr and Weitao - page 108. But, from the expression of \rho_{1} given ...
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Evidence for indistinguishable particles

What's the simplest evidence for indistinguishable particles? Is there any evidence/experiment without resorting to large ensemble/statistical results?
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Exchange interaction and nuclear fusion

Most texts about nuclear fusion say that the reason it is so hard to get protons to fuse is the strong Coulombic repulsion between them. However, it seems to me that at close distances, protons should ...
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Why the superexchange interaction is antiferromagnetically favorable?

From Stephen Blundell's book 'Magnetism in Condensed Matter', the superexchange interaction between two magnetic ions mediated by non-magnetic ions is generally antiferromagnetic. In his book, he ...
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Magnon spectrum with in-plane Dzyaloshinski-Moria interraction

I'm attempting to derive a magnon spectra using first principles. In-plane DMI is considered in my system. $z$ axis is out of plane. First of all I wrote a Hamiltonian for interacting spins with two ...
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Value of Heisenberg exchange constant

I am aware that for two interacting electrons, the portion of the Hamiltonian $\hat{H}_{\text{ex}}$ is equal to$$J\begin{pmatrix}\frac14&0&0&0\\0&-\frac14&\frac12&0\\0&\...
slithy_tove's user avatar
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How do I find the exchange energy from the effective Hamiltonian?

I've just recently started studying noise in singlet-triplet qubits and the exchange interaction (as a function of detuning ${\epsilon}$ and tunnel coupling ${t_c}$) seems fundamental in many studies. ...
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Quantum measurement and exchange interaction

If we consider a two-electron system, the operators (say, momentum or spin) for the first and the second electron are commuting, and so, these values may be considered measurable together. Moreover, ...
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Why classical mechanics is not able to explain the net magnetization in ferromagnets?

Why classical mechanics is not able to explain the net magnetization in ferromagnets? why does exchange interaction can explain net magnetization in Ferromagnets, which is purely quantum mechanics??
SAROJ KUMAR MISHRA's user avatar
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Why Hund's first rule neglect one of the spin triplet states?

For two electrons, the spin triplet states allow their spacial wavefunction to be antisymmetric with respect to the exchange of particles, and can minimize the coulomb repulsion energy because larger ...
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Why Does Exchange Symmetry Stabilize Quantum Systems?

When trying to solve Schrödinger equation approximately, we usually represent wavefunction of the system as the Slater determinant of some set of spin orbitals to take into account that fermions (...
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Spin Hamiltonian for 2 electron system

I am currently studying exchange interaction and came across the spin operator in Ashcroft and Mermin Chapter 32 page 680 which states that the spin hamiltonian can be defined as: ...
VATSAL JAIN's user avatar
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What is the value of the exchange field in the 3d ferromagnets ($\rm Ni, Fe, Co$)?

I have been trying to find the values of the exchange field for Ni, Co and Fe. This website mentions, "Exchange forces are very large, equivalent to a field on the order of 1000 Tesla" https:...
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How can the exchange interaction make electron spins parallel?

Electrons repel by Coulomb interaction. When they get too close, Pauli exclusion principle ("Exchange interaction") becomes important. If their spins are parallel, they are further "...
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Question About Exchange

Is the Exchange term, for example in a set of Hartree-Fock equations for a solid, to be interpreted as arising from electrons actually, physically, exchanging positions constantly? So, for a metal, I ...
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Mathematical expression of the coordinate exchange operator

So I know that the total exchange operator is the product of the coordinate, spin and isospin exchange operators, as, \begin{equation} P_{12} = P_{12}^r P_{12}^\sigma P_{12}^\tau \end{equation} The ...
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Effect of Exchange Interaction on Magnetism

My physics book says that the magnetic properties of ferromagnetic substances are a resultant of a process called exchange coupling in atoms, but unfortunately does not explain any why or how it does ...
Agrim Arsh's user avatar
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What is the “exchange energy of electrons”?

First, do not try to give me the perplexing explanations involving higher QM. I am new to QM, so please give a gentle explanation. Now, my textbook see page 36 states that electrons of degenerate ...
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Finding general information about the Dzyaloshinskii-Moriya interaction (DMI)

I have to do an assignment on the Dzyaloshinskii-Moriya interaction for a magnetism (in condensed matter) course that I am following. My teacher said that this topic is rather popular, but I cannot ...
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Time evolution of spin with Anti-symmetric (Dzyaloshinkii-Moriya) interaction

I am trying to simulate the time evolution of a spin in spin chain interacting via Dzyaloshinkii-Moriya interaction. The Hamiltonian is of the form $$H_{A}=J_{A}\sum_{i}(S^{x}_{i}S_{i+1}^{y}-S^{x}_{i+...
alpha_prime's user avatar
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Sign of exchange integral in GKA (superexchange) rules

I was reading about the super-exchange mechanism that leads to magnetic order (Antiferromagnetic or Ferromagnetic) in insulating solids here. Kanamori breaks down the mechanisms in several specific ...
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Different types of magnetic exchange

I am a bit confused about the mechanisms of different types of exchange. Mainly, I am trying to understand mechanisms that lead to magnetic ordering and I came across several different types of ...
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Are combined fermion wavefunctions still antisymmetric after wavefunction collapse?

If we have two electrons in a state $|\psi\rangle=\frac{1}{\sqrt2}[|\uparrow\downarrow\rangle+|\downarrow\uparrow\rangle]$ and we measure the spin of the first electron to be up, does the wavefunction ...
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Can a photon's angular momentum couple to an electron spin, to cause a spin-flip (thus allowing intersystem crossings)?

Been reading up on intersystem crossing and have gotten rather confused by: a photon possesses an angular momentum of $h/2\pi$ so it can couple to an electron spin and in principle induce any ...
Voetvoet's user avatar
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Could the Fermi statistic be a force?

I'm aware that, according to the Pauli principle, identical fermions obey the Fermi-Dirac statistics, so they don't occupy the same state because they just can't, it's simply how they behave. I'm ...
Mauro Giliberti's user avatar
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The Hund's J - Why can this be quantified?

I was reading on the the implementation of Hubbard 'U' in Density Functional Theory. The Hubbard 'U' can be thought of as a parameter that accounts for the on-site electron-electron interactions in ...
livars98's user avatar
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Coupling of two spin half particles

If there are two electrons coupled by interaction having hamiltonian H=A*S1*S2 where S1 and S2 are spin angular momentum operators of two electrons, we know we have four possible eigenstates for the ...
Siddharth Jain's user avatar
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Does the (non-)collision of two fermion wave packets demonstrate that there is no exchange "force"?

In the paper "Quantum statistics: Is there an effective fermion repulsion or boson attraction?" by Mulling and Blaylock (2003), it is claimed that We can demonstrate there is no real force due to ...
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Exchange has closed form also in DFT?

I have heard from my lecturer that in the context of DFT, the exact exchange energy has a known closed form, even though it is not a functional of the density. I have been trying to figure out what ...
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DFT: When would one use a LDA over a GGA method?

Computationally using Density Functional Theory (DFT), is there any examples where Local Density Approximation (LDA) would be preferred over using Gradient Generalized Approximation (GGA) methods for ...
furg berful's user avatar
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Why don't all elements with unpaired electrons become ferromagnetic?

As a necessary condition, ferromagnetism in elements requires the existence of unpaired electrons. However, all elements with unpaired electrons are not ferromagnetic, e.g., metals such as aluminium ...
Solidification's user avatar
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Which mechanism causes ferromagnetism in iron?

There are at least three different mechanisms which can give rise to ferromagnetic order in iron. First is due to the band electrons called band magnetism or itinerant magnetism which is an exchange ...
Solidification's user avatar
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1 answer
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Why an insufficient overlap cause vanishing exchange interaction?

Why should the exchange interaction vanish if the atoms do not have sufficient overlap in their overfunctions? For exchange interaction not to vanish, the only requirement seems to be that the ...
Solidification's user avatar
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Symmetry in Fock-space 2-body interaction

The simplest two body interaction term for fermions is $$H = \sum_{ijkl} U_{ijkl} a_i^\dagger a_j^\dagger a_k a_l$$ and I'm trying to determine the symmetries on $U$. Unfortunately I keep getting ...
Alex Meiburg's user avatar
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To get short-range interaction from long-range interaction

Interactions in Condensed matter systems are almost exclusively the electromagnetic interactions which are long-range. But it often gives rise to short-range interactions in systems e.g., exchange ...
Solidification's user avatar
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Exchange Interaction Time Evolution

This is a hypothetical based on a result in Griffiths (which is my level of QM understanding). In it, he derives an "exchange force" - two particles states A and B, a two-particle state composed of ...
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Exchange stiffness for HCP

I am studying the exchange interaction, which can be described with the Heisenberg Hamiltonian: $\hat{H} = -\sum_{i,j}J_{ij}\hat{\mathbf{S_i}}\cdot \hat{\mathbf{S_j}}$ In the framework of constant ...
mickeymar's user avatar