Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.

Questions tagged [quantum-spin]

Fundamental characteristic property of particles which together with orbital angular momentum acts as the generator of rotations and which doesn't have a classical equivalent but is sometimes compared to and contrasted with classical intrinsic angular momentum.

Filter by
Sorted by
Tagged with
0
votes
1answer
614 views

Is the Singlet state for Helium with 2 electrons symmetric rather than anti-symmetric as is meant to be for fermions?

I'm looking at two-electron Helium atoms where one electron is in the ground state (due to if it were in other states, it's de-excitation would simply lead to the ionization of the electron). The ...
0
votes
1answer
1k views

How do I find an expectation value for an electron's magnetic moment?

Given a spin state: $|s\rangle$ = some linear combination of $|\uparrow\rangle + |\downarrow\rangle$ possibly with an imaginary component. How do you get from the definition of a magnetic momentum ...
0
votes
1answer
387 views

In a Stern-Gerlach measurement, does passing particles through the B field influence their spin state?

This question is similar to this post and was influenced by this discussion as well. Assume a Stern-Gerlach apparatus oriented along the z-axis acts as a measurement on the basis of the z-component ...
0
votes
1answer
197 views

What exactly is quantum spin? [duplicate]

What is "spin" as it relates to subatomic particles? I've heard that it's similar to angular momentum but I've also heard that's not completely the case.
0
votes
0answers
145 views

representation of spinors

I am trying to get from the abstract representation of Spinors, as wave functions $|\Psi \rangle$ in the base of tensors products $| S_z \rangle \otimes | x \rangle$ of eigenvectors of the spin ...
0
votes
0answers
345 views

Does point group symmetry also act within “spin space” for a lattice spin system?

As an example, let's consider a quantum spin system on a 2D square lattice. The lattice point group symmetries include $C_4$ rotation, parities, etc.... And let's take $C_2$ symmetry (2-fold rotation) ...
0
votes
1answer
143 views

Why does a spinning nucleon generate a magnetic field?

I am trying to understand how NMR works, but I am not sure why a spinning nucleon produces a magnetic field. Is this a consequence of the quark structure inside?
0
votes
0answers
773 views

Spin, parity, etc. conservation in decays/reactions

I have a long list of short physics questions I'm reviewing, and there are several that ask about whether certain decays or reactions are allowed. Clearly these questions are testing my knowledge of ...
0
votes
0answers
96 views

Two state Hubbard modell

I am given the two state Hamiltonian $$ H = U \sum_{j \in \{L,R\}} n_{j \uparrow}n_{j \downarrow} - t \sum_{\sigma \in \{\uparrow,\downarrow\}}(a_{L \sigma}^{\dagger}a_{R \sigma} +a_{R \sigma}^{\...
0
votes
1answer
136 views

J-coupling constants and nuclei with zero total angular momentum

The Wikipedia page on J-couplings states that Scalar or J-couplings (also called indirect dipole dipole coupling) are mediated through chemical bonds connecting two spins. It is an indirect ...
0
votes
0answers
54 views

Could we imagine spin as rotating probability densities (orbitals) in a kind of expanded orbital model?

I know there is no spin in orbital model. And it is always said there is no visualization for the spin. But why not just let the oribtals rotate with 4D quaternions in some 3D dynamic model?
0
votes
0answers
43 views

A question on lowering the total spin

Is there a way to lower the total spin of the state and fixing the $S_z$ rather than lowering the $S_z$ by spin ladder operator? Or in other words, how to connect the $S=1$ state with $S=2$ or $S=0$ ...
0
votes
1answer
63 views

Spinning of the Earth [duplicate]

I was just wondering What would happen if the earth spins the other way around purely interms of Physics ?
0
votes
1answer
363 views

How can a black hole have spin?

How is it possible, or even meaningful, to say that a black hole has spin? (Tangentially, if the singularity is assumed to be a point, it must have either zero or infinite angular momentum, in both ...
0
votes
0answers
120 views

How to find an action of $(\hat {\sigma} \cdot \hat {\mathbf L} )$ on spherical spinors?

Let's have the spherical spinors $\psi_{j, m, l = j \pm \frac{1}{2}}$, $$ Y_{j, m, l = j \pm \frac{1}{2}} = \frac{1}{\sqrt{2l + 1}}\begin{pmatrix} \pm \sqrt{l \pm m +\frac{1}{2}}Y_{l, m - \frac{1}{2}} ...
0
votes
1answer
205 views

Geometric Interpretation of Rotated basis of Hamiltonian and collective Dicke states

Suppose I start with a basis of states for a two spin-1/2 particle system, namely, $\{\left|\uparrow\uparrow\right\rangle, \left|\downarrow\downarrow\right\rangle, \left|\uparrow\downarrow\right\...
0
votes
0answers
248 views

What the quantum spin refers to? How we calculate the angular momentum $\omega$ from the spin quantum number?

How we calculate the angular momentum $\omega$ from the spin quantum number, to know how fast a particle rotating on its own axis?
0
votes
0answers
65 views

What physical value is described by following operator?

Let's have the system of point-like non-interacting particles and it's own angular momentum $$ \mathbf L_{1} = \mathbf L - [\mathbf R_{E} \times \mathbf P], $$ where $\mathbf R_{E}$ - center of energy ...
0
votes
0answers
321 views

Ground and first excited state of non interacting spin system Hamiltonian

For a non interacting spin system containing two $\frac{1}{2}$ spin particles I am trying to determine its Hamiltonian. If the energy of a up spin is $+\mu {\bf B}$ and a down spin is $-\mu {\bf B}$, ...
0
votes
0answers
95 views

What exactly is the spin of a particle? [duplicate]

Possible Duplicate: What is spin as it relates to subatomic particles? I'm having a hard time grasping the concept of spin, my textbook describes it very vaguely: Stable matter contains just ...
0
votes
0answers
64 views

If Earth Were Filled with a Compressible Fluid and Spun Really Fast, What Hollow Would Form? [duplicate]

Possible Duplicate: What nonlinear deformations will a fast rotating planet exhibit? This is really a basic physics question that I wanted to check myself on because I'm not entirely sure of the ...
0
votes
2answers
96 views

Does the spin has a determinate value in magnetic field?

Consider a 1/2 spin particle like proton in magnetic field $B$ in the $z$ direction with strength as high as in NMR appliances. Then the anomalous Zeeman Effect occurs. And the particle has two ...
0
votes
1answer
58 views

Relation between quantum numbers $j$ and $\ell$

I'm given the following problem: "Consider an atom with orbital angular momentum $l$. What are the possible values of the total angular momentum quantum number $j$? Treat the case of $\ell = 0$ ...
0
votes
1answer
272 views

Why do nuclei precess in magnetic fields?

I understand that a classical bar magnet will precess about the axis of an external magnetic field. Whilst researching NMR, I have read that nuclei with half-integer spin which are subject to an ...
0
votes
1answer
146 views

What is the difference between a material in which the Rashba effect occurs that is not a topological insulator, and one is a TI?

I am working on topological insulator (TI) materials and I always have trouble understand the time reversal symmetry, spin orbit coupling in TI. As to my understanding, the TI material property ...
0
votes
2answers
3k views

Why magnetic field lines and force are not orthogonal with magnets?

The below explanation why magnetism exists is superb in this video. The explanation about magnets is also great in this video. A magnet has atoms with unpaired electrons forming mini magnets. The ...
0
votes
2answers
623 views

Why electron has spin angular momentum?

The classical concept of electron spin is wrong. From Stern Gerlach experiment we have seen that two separate beams are produced and that is why it is considered that electron has some property in ...
-1
votes
1answer
2k views

Commutator with Pauli spin matrices and the momentum operator

How is $\left[\vec\sigma \cdot \vec p, \vec \sigma \right]$ proportional to $\vec \sigma\times \vec p$, where $\sigma$ are the Pauli spin matrices and $p$ is the momentum operator?
-1
votes
2answers
65 views

What is the (triplet) eigenstate for two electrons? [duplicate]

Let's assume I have a harmonic oscillator which is one dimensional. What is my plan is to work the the two electron's spin states and my requirement is that they have to be in the triplet sates. Lets ...
-1
votes
2answers
127 views

What does Quantum Spin Cause? [duplicate]

How do particles with different Quantum Spin Numbers interact differently with other matter? What does spin cause? I understand that electrons etc act as if they are spinning my emitting a magnetic ...
-1
votes
1answer
80 views

Why is there no $1S_{-1/2} $ state of the hydrogen atom?

Heyho, i found this term scheme for the hydrogen atom: https://upload.wikimedia.org/wikipedia/commons/9/94/Wasserstoff_Aufspaltung.svg I was wondering why there is only a $1S_\frac{1}{2}$ state and ...
-1
votes
1answer
54 views

Why is Quantum Spin measured in JouleSeconds?

To my knowledge, the unit of quantum spin is h-bar on two. This has units of Joules times seconds divided by radians. The radians part makes sense to me, the Joules Seconds part, does not. Why is ...
-1
votes
1answer
372 views

Difference between angular momentum $L$ and $J$ in quantum mechanics

what is the difference between angular momentum L and generalized angular momentum J and their components?
-1
votes
2answers
86 views

What is $\vec \sigma$ in the context of spin?

Leonard susskind's book, quantum mechanics, the theoretical mimimum, statea that we can derive the spin operator $$\sigma_n=\sigma_x n_x + \sigma_y n_y + \sigma_z n_z$$ Where the $\sigma_i$ are spin ...
-1
votes
1answer
129 views

Spin (for chemists) for 100th time here on the forum [closed]

EDIT: Okay so I see the question was bit unclear. I know about matrices as far as we have used them but we never used any group theory. Determinants like slater determinants are used in chemistry, ...
-1
votes
1answer
151 views

No need for spin?

Here's a cool idea: we don't need spin: recall that a quantum field arises from an attempt to construct an object that transforms unitarily under $SO(1,3)$ (i.e. by choosing a representation). A ...
-1
votes
4answers
97 views

Is the oxygen molecule $O_2$ fermion or boson?

I ask something makes me confused. In generating singlet oxygen molecule, I initially thought a light (photon) can excite the ground state oxygen molecule. However, my colleague said that process is ...
-1
votes
1answer
80 views

Can we use the Pascal triangle as an aid to construct superpositions of wavefunctions corresponding to $n$ electron spins?

Suppose we have n electrons and want to construct the wavefunction corresponding to the spins of the electrons. Can we construct this wavefunction (in the $(s_1,s_2,s_3 ... s_n)$ representation, so ...
-1
votes
1answer
23 views

Question about the spin of the antiparticle of $Δ^-$

Ι came across a statement in a physics book that the spin of the antiparticle of baryon $Δ^-$ is 1/2. I know that the spin for regular $Δ^-$ is 3/2, and - as far as I know - the spin of particles and ...
-1
votes
1answer
116 views

Basic question on spin wavefunction

In my textbook, I am told that the $\Delta$ is a spin-3/2 particle made up of three spin-1/2 quarks. For a state with definite spin $m=-1/2$, I'm given that the spin wavefunction $$\dfrac{1}{\sqrt{3}}(...
-1
votes
1answer
36 views

Fused Electrons Spin [closed]

If it was possible to make two electrons fuse, would it also be possible to increase the magnitude of that object's spin since it is not an elementary particle?
-1
votes
1answer
2k views

Like charges and unlike charges [duplicate]

Like charges repel and unlike charges attract. But when do like charges attract and unlike charges repel?Please cite an example to justify it.
-1
votes
1answer
150 views

What is the physical difference of a symmetric and antisymmetric state superposition?

I am inclined to think that the symmetric superposition implies that both states have the same global phase and that in the antisymmetric one they are completely dephased. By symmetric and ...
-1
votes
1answer
112 views

How can a neutrino have same spin as an electron?

Is there any explanation or just any guess about how a particle which is about a billion time smaller than an electron can have same vaule of spin: $\hbar$/2? The spin is an intrinsic property, that ...
-1
votes
1answer
222 views

superposition of states, spin 1/2

Something was wrong... Two particles, their spin are 1/2. The hamiltonian is $H=\gamma s_1 \cdot s_2$ At t=0, the state $|\alpha(0)>$ is such as $s_{1z}|\alpha(0)>=\hbar/2 |\...
-1
votes
1answer
64 views

Question regarding entanglement

Could the paradoxical nature of entanglement be the result of a change in the nature of quantum properties, or an incomplete understanding of such, instead of non-locality?
-1
votes
2answers
507 views

Searl effect generator simulation

This is an scheme of SEG: https://www.youtube.com/watch?v=pUUvhuQtba4 https://www.youtube.com/watch?v=wAMrTxMzrds This mechanism change the electrons around the conversor. Would be really nice to ...
-1
votes
1answer
188 views

Spin orientations

The concept of spin is purely a quantum mechanical effect, it is restricted to given values in given orientations. If hypothetically spin were a classical concept yet still of a fixed value, would its ...
-1
votes
0answers
11 views

Encode classical information (cbits) into qubits and apply depolarization channel

I am a newbie in quantum information area and have just started to know basic concepts of quantum mechanics. I was working out an example of how cbits can be turned into qubits and then apply a ...
-1
votes
1answer
29 views

What is the term for a particle spin's uncollapsed position? What is the orbiting “thing”?

I'm not sure if I have the correct visual model, but I imagine that a particle spin can be represented by a single point on the orbit, or by a superposition state (like a random plane through a corner ...