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Add a spin irreducible operator in a spinful fermionic system with U(1) charge and SU(2) spin symmetry #23
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Hi Yong-Yue Zong, Thanks for the suggestion! I am definitely very happy to add this, would you have a suggestion for a good name? In hindsight, naming these functions with a single letter is probably not very future-proof, as Best, |
How about |
I would also need a non-unicode version, as there still are some systems (terminals, editors, ...) where these are very hard to type. I don't have too much time the next week, any chance you could file a PR with this? |
Of course |
Hi Lukas,
Thanks for your package!$\hat{S}=\sum_{\sigma\sigma'}f^\dagger_\sigma\vec{\sigma}f_{\sigma'}=(-S^{+}/\sqrt{2},S^{z},S^{-}/\sqrt{2})$ in a spinful fermionic system with U(1) charge and SU(2) spin symmetry. This could be beneficial as we consider magnetic properties in electronic systems.
I suggest to add a spin irreducible operator
With Wigner–Eckart theorem, we have
where the quantum number are labeled as$(q_n; S, S_z)$ and $C^{1/2}_{1/2,1}$ is the CG coefficients with dimension $=2\times 3 \times 2.$ $S^{z}$ and $S^{+}$ are equivalent with this one because the reduced matrix element $\langle 0;1/2|S^{0;1}|0;1/2\rangle$ is independent of quantum number $S_z$ .$\langle 0,1/2|S^{0;1}|0;1/2\rangle = \sqrt{3}/2$ .
The other two equations about
Here, we have
We can construct the spin irreducible operator$\hat{S}$ as
Thank you again for your nice package!
Sincerely yours
Yong-Yue Zong
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