# 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.

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### Simple models with non-abelian anyons [closed]

It is well known, that in 1d and 2d there are particles with anyone statistics. Which 1d and 2d models have such excitations? Which model with anyons is simplest?
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### Spherical tensor operators relation to spin operators

I am reading a research paper discussing theoretical calculations of electron paramagnetic resonance parameters (EPR)*. In the section about higher-order EPR parameters, it states that according to ...
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### How do crystals protect electronic spin qubits?

Defects in SiC crystals demonstrated entanglement between electronic spin qubits at room temperature. But do we need a crystal to protect the state? My understanding is that crystals, being uniform ...
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### Total spin on a two particle system

How can I know the total spin of a given state quickly? I first encountered this problem when proving the Clebsch-Gordan series. Consider a two particle system (to make it easier, lets say identical ...
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### Spin of skyrmion

Baryons can be considered as solitions in Skyrme model(See also this post.): Such Lagrangian haven't any information about number of colors. Bosonic or fermionic nature of baryons depends on number ...
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### How exactly does an electrons spin cause it to have a magnetic moment?

So I understand you can rearrange the equation for a single electron orbiting in a circle $(\mu=evr/2)$ and substitute in the associated velocity for angular momentum $(v=L/mr)$ where angular momentum ...
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### Physical description of spin wave theory and Bogoliubov transformation

I am trying to understand how spin-wave theory explain the behaviour of a spin-wave in a spin system. To clarify my question, I will start with a simple case of a antiferromagnet (AFM). The ...
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### Why must the ground state of helium be a singlet?

Every reference I have seen, including e.g. question (a) on page 5 of these notes or the comments in the answer of this post, use a hand-wavy perturbation theory argument for non-degeneracy of the ...
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### Is $\boldsymbol{\nabla}\cdot\mathbf{S}$ zero?
There exists a classical definition of the orbital angular momentum, $$\mathbf{L}=\mathbf{r}\times\mathbf{p}$$ Due to this definition, the following quantity is identically zero, \boldsymbol{\nabla}\...
I'm having some trouble with understanding the distinction between spinful and spinless time-reversal in a real materials context. 1) Does spinful time-reversal (e.g. $\mathcal{T}^2 = -1$) imply spin-...