pauli matrices in yambo

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pauli matrices in yambo

Post by batman » Mon Jun 26, 2023 3:36 pm

Dear Developers,

The sigma_y matrix defined in "yambo/src/modules/mod_D_lattice.F" is not correct. As Fortran in column major, reshaping [1,2,3,4] will give ([[1 3],[2 4]])
so the matrix is currently defined as -sigma_y(actual). I can see that in one of the Tait-Bryan angles (beta) defined in "yambo/src/setup/build_spin_sop.F" lacks minus sign. I guess the minus was removed to compensate this. When rotating spinors wave functions with time reversal symmetry, it picks up an additional phase of -1 (which does not effect the results due to gauge arbitrary ness). I also see some other instances where sigma_y is used. Is it a bug or was it intentionally coded in this way?

Best regards,
Muralidhar Nalabothula
Doctoral student at Department of Physics and Materials Science,
Université du Luxembourg

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Davide Sangalli
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Re: pauli matrices in yambo

Post by Davide Sangalli » Mon Jun 26, 2023 3:46 pm

I opened an issue:
Better to double check this.
I do not think it was coded like that on purpose.

Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre

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